Neutralising antibodies to the major exotoxins tcda and tcdb of clostridium difficile

ABSTRACT

This present invention describes the derivation and selection of antibodies capable of neutralising the major exotoxins; TcdA and TcdB of  Clostridium difficile . The invention also describes novel neutralisation and antigen binding properties of individual Mabs and mixtures thereof.

The present invention relates to antibodies to exotoxins of Clostridiumdifficile, for example TcdA and TcdB, pharmaceutical compositionscomprising the same, processes of producing said antibodies andcompositions and use of the antibodies and compositions in treatmentand/or prophylaxis, in particular treatment or prophylaxis ofClostridium difficile infection, pseudomembranous colitis, fulminantcolitis and/or toxic mega colon.

The two major exotoxins TcdA and TcdB have been established as the majorpathogenicity determinants of Clostridium difficile in a large number ofin vitro and in vivo studies. Non-toxigenic strains are not pathogenicto animals and man (1, 2). To date a clear understanding of the role ofbinary toxin has yet to be established (3).

Both toxins are entero- and cyto-toxic, but the balance of evidencesuggests that TcdA is a more powerful enterotoxin than TcdB, whilst TcdBis typically observed to be ˜1000× more cytotoxic than TcdA (4). Whilstboth toxins are capable of inducing an inflammatory response, TcdAappears to aid the migration of the more inflammatory TcdB deeper intothe gut mucosa (5).

In toto, a large collection of data generated for over 30 years supporta model where both toxins are likely to be important in the humandisease process. It is probable that TcdA initiates early (i.e. beforeTcdB) and rapid (i.e. 1-3 hours) gut damage through loss of tightjunctions and destruction of villi tips and hence diarrhoea, probablythrough albumin driven fluid loss. This damage to the integrity of thegut lining enables TcdB to exert its superior molar potency (TcdB istypically cited as being 1000× more cytotoxic than TcdA) more rapidlyand effectively (i.e. deeper into tissue, alternative cellular targetsand damaging systemically accessed organs). Either toxin can beeffective alone in vitro on human or animals cells and tissues. Eithertoxin can be effective alone in vivo in animals depending upon othereliciting factors such as mechanical damage, barrier overload and hostspecific sensitivities. It is now clear that in hamsters at least eitherTcdA or TcdB alone delivered by a Clostridium difficile gut infectioncan cause death (1). It is well established that A−B+ strains arecapable of causing symptoms and death in humans (6,7). However, themajority (˜95%) of clinical strains are A+B+ hence drugs aimed attreating Clostridium difficile infections (CDI) must be capable ofneutralising the activities of and clearing both toxins effectively.

CDI is most typically a nosocomial infection of older patients or thosewith complicating co-morbidities. However, an increase in communityacquired infections has been noted. Infection is almost alwaysassociated with or induced by use of broad spectrum antibiotics.Healthcare associated costs are estimated to be in excess of $1 bn perannum in the US alone. These costs are primarily due to patients havinglonger hospitals stays. Current therapies involve the use of antibioticssuch as clindamycin, vancomycin or fidaxomicin which kill theClostridium difficile cells within the gut. Current therapies addressthe bacterial infection but do not deal with or prevent directly thesignificant pathogenesis caused by TcdA and TcdB which are majorcontributors to CDI symptoms and mortality.

CDI symptoms in humans include mild to severe diarrhoea,pseudomembranous colitis (PMC) and fulminant colitis or so called toxicmega colon. Death results in 5-15% of patients receiving current bestcare. Thus at the present time there is no specific therapy available topatients to prevent the damage and injury caused by C. difficile toxinsafter infection.

Raising an antibody response through vaccination and parenteraladministration of polyclonal and monoclonal antibodies have all beenshown to be capable of protecting animals from symptoms of diarrhoea anddeath (8-15). Early studies in hamsters suggested that antibodiesagainst TcdA alone were all that was necessary for protection. However,use of strains functionally deleted for TcdA or TcdB demonstrate thateither toxin is capable of causing disease in hamsters, but that bothtoxins together are more effective (1).

For therapeutic applications, monoclonal antibodies (Mabs) can offerefficacy, safety, manufacturing and regulatory advantages over serumderived polyclonal antibodies or serum derived hyper-immune sera. Forthese reasons Mabs are usually the preferred option for therapeuticproducts.

There have been a number of attempts to generate protective Mabs againstTcdA and TcdB. The most advanced of these in the clinic is a mixture of2 IgG1 Mabs, one against each TcdA and TcdB originally called CDA1 andMDX1388 developed by MBL and Medarex. They were demonstrated to beunable to fully protect hamsters in models of acute or relapseinfections (15). This Mab combination is now being developed as MK3415Aby Merck Inc. In a human phase II trial MK3415A resulted in astatistically significant reduction in disease recurrence (p=0.006) (seealso Lowy et al., NEJM (2010) 362: 197-205) but did not affect theduration/severity of diarrhoea or death rates (16). This may mean thatthese antibodies may only be useful for preventing recurrence ofinfection. Recurrence of infection results in approximately 25% ofpatients. Thus there likely to be a significant patient population inwhich these antibodies are not effective.

In order to be able to have a positive influence upon diarrhoea (forexample as a result of acute damage to gut tight junctions due to TcdA)and death (for example resulting from prolonged poor nutritional status,dehydration stress and initiation of an inflammatory cascade, widespreadanatomical damage to the gut lining and possibly damage to distantorgans due to systemic toxin TcdB more so than TcdA) Mabs are requiredwith superior affinity, toxin neutralisation, superior prevention ofloss of TEER (trans-epithelial electrical resistance), antigendecoration and antigen immune clearance.

SUMMARY OF THE PRESENT INVENTION

The present invention provide a Mab(s) with a very high level of potencyin vitro and in vivo which have the potential to have an impact uponduration and severity of diarrhoea and death rate in humans sufferingfrom Clostridium difficile infection (CDI).

In one embodiment there is provided a monoclonal antibody specific toantigen TcdA or TcdB, wherein the antibody has high affinity for thetarget antigen and is suitable for reducing the duration and/or severityof diarrhoea and morbidity in a patient with Clostridium difficileinfection or at risk of said infection.

In one embodiment there is provided a Mab specific to TcdA or TcdB, or apopulation of at least two Mabs at least one of which is specific toTcdA and at least one of which is specific to TcdB, wherein the EC₅₀ ofthe or each antibody or the combination of antibodies is 200 ng/ml orless, for example 150 ng/ml or less such as 100 ng/ml.

The antibodies of the present disclosure are useful because they arelikely to provide a means of treating the severity and duration ofsymptoms of a primary infection such as diarrhoea in a patient orpreventing death and not just prevent the reoccurrence of diseasesymptoms.

In at least some embodiments the antibodies according to the presentdisclosure show no reduction in potency in the presence of highconcentrations of toxin.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

Specific as employed herein is intended to refer to an antibody thatonly recognises the antigen to which it is specific or an antibody thathas significantly higher binding affinity to the antigen to which isspecific compared to binding to antigens to which it is non-specific,for example 5, 6, 7, 8, 9, 10 times higher binding affinity.

Binding affinity may be measured by standard assays such as surfaceplasmon resonance, such as BIAcore.

In one embodiment the EC₅₀ is less than 75, 70, 60, 65, 55, 50, 45, 40,35, 30, 25, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1.5 ng/ml Clostridiumdifficile infection in cell culture assays and the patient. This issignificantly lower (more potent) than known antibodies and is thoughtto be a major factor as to why the antibodies of the present disclosurehave a significant and positive impact on survival of subjects receivingtreatment.

As employed herein potency is the ability of the antibody to elicit anappropriate biological response, for example neutralisation of thedeleterious toxin effects, at a given dose or concentration. Examples ofpotency include the percent maximal neutralisation of toxin activity(extent of protection), the lowest relative concentration of Mab toantigen (e.g. EC₅₀), the speed and durability of neutralisationactivity.

In cell culture assays neutralisation might be observed as one or moreof the following: prevention of binding of toxin to cells,immunoprecipitation of toxin from solution, prevention of loss of cellform and shape, prevention of loss of cytoskeletal structures,prevention of loss of cell monolayer tight junctions andtrans-epithelial electrical resistance, prevention of cell death,apoptosis and production of pro-inflammatory cytokines such as TNFα,IL-1β, IL-6 and MIP1α.

In tissue section and explant assays neutralisation may, for example beobserved as prevention of necrosis and/or oedematous fluid accumulation.

In in vivo assays neutralisation may be observed as one or more of thefollowing: prevention of fluid accumulation in ligated ileal loops andprevention of gut tissue necrosis, diarrhoea, pseudo-membrane formationof death of animals,

Thus in one embodiment there is provided an antibody (for example ananti-toxin A antibody) comprising a CDR, such as 1, 2, 3, 4, 5 or 6CDRs, selected from:

SEQ ID NO: 1 QASQSISNALA SEQ ID NO: 2 SASSLAS SEQ ID NO: 3 QYTHYSHTSKNPSEQ ID NO: 4 GFTISSYYMS SEQ ID NO: 5 IISSGGHFTWYANWAKG SEQ ID NO: 6AYVSGSSFNGYAL

In one embodiment sequences 1 to 3 are in a light chain of the antibody.

In one embodiment sequences 4 to 6 are in a heavy chain of the antibody.

In one embodiment SEQ ID NO: 1 is CDR L1, SEQ ID NO: 2 is CDR L2 and SEQID NO; 3 is CDR L3.

In one embodiment SEQ ID NO: 4 is CDR H1, SEQ ID NO: 5 is CDR H2 and SEQID NO; 6 is CDR H3.

In one embodiment SEQ ID NO: 1 is CDR L1, SEQ ID NO: 2 is CDR L2, SEQ IDNO; 3 is CDR L3, SEQ ID NO: 4 is CDR H1, SEQ ID NO: 5 is CDR H2 and SEQID NO; 6 is CDR H3.

In one embodiment there is provided a variable region, such as a lightchain variable region with the following sequence (Antibody 922anti-toxin A antibody; Light chain Variable region sequence) SEQ ID NO:7:

DPVMTQSPSTLSASVGDRVTITCQASQSISNALAWYQQKPGKAPKLLIYSASSLASGVPSRFKGSGSGTEFTLTISSLQPDDFATYYCQYTHYSHTSKNP FGGGTKVEIKwherein the CDRs are underlined and construct is referred to herein as922.g1 VK (gL1).

The polynucleotide sequence encoding SEQ ID NO: 7 is shown in FIG. 1 andSEQ ID NO: 8 therein.

In one embodiment there is provided a variable region, such as a heavychain variable region with the following sequence (Antibody 922anti-toxin A antibody heavy chain variable region sequence) SEQ ID NO:9:

EVQLVESGGGLVQPGGSLRLSCAASGFTISSYYMSWVRQAPGKGLEWIGIISSGGHFTWYANWAKGRFTISSDSTTVYLQMNSLRDEDTATYFCARAYVS GSSFNGYALWGQGTLVTVSwherein the CDRs are underlined and construct is referred to herein as922.g1 VH (gH1)

The polynucleotide sequence encoding SEQ ID NO: 9 is shown in FIG. 1 andSEQ ID NO: 10 therein.

In one embodiment the antibody comprises the variable regions shown inSEQ ID NO: 7 and 9.

Thus in one embodiment there is provided an antibody (for example ananti-toxin A antibody) comprising a CDR, such as 1, 2, 3, 4, 5 or 6CDRs, selected from:

SEQ ID NO: 11 QASQSISNYLA SEQ ID NO: 12 SASTLAS SEQ ID NO: 13QYSHYGTGVFGA SEQ ID NO: 14 AFSLSNYYMS SEQ ID NO: 15 IISSGSNALKWYASWPKGSEQ ID NO: 16 NYVGSGSYYGMDL

In one embodiment sequences 11 to 13 are in a light chain of theantibody.

In one embodiment sequences 14 to 16 are in a heavy chain of theantibody.

In one embodiment SEQ ID NO: 11 is CDR L1, SEQ ID NO: 12 is CDR L2 andSEQ ID NO: 13 is CDR L3.

In one embodiment SEQ ID NO: 14 is CDR H1, SEQ ID NO: 15 is CDR H2 andSEQ ID NO; 16 is CDR H3.

In one embodiment SEQ ID NO: 11 is CDR L1, SEQ ID NO: 12 is CDR L2, SEQID NO: 13 is CDR L3, SEQ ID NO: 14 is CDR H1, SEQ ID NO: 15 is CDR H2and SEQ ID NO; 16 is CDR H3.

In one embodiment there is provided a variable region, such as a lightchain variable region with the following sequence (Antibody 923anti-toxin A antibody; Light chain Variable region sequence) SEQ ID NO:17:

DVVMTQSPSSLSASVGDRVTITCQASQSISNYLAWYQQKPGKVPKLLIYSASTLASGVPSRFKGSGSGTQFTLTISSLQPEDVATYYCQYSHYGTGVFGA FGGGTKVEIKwherein the CDRs are underlined and construct is referred to herein asCA923.g1 gL1

The polynucleotide sequence encoding SEQ ID NO: 17 is shown in FIG. 1and SEQ ID NO: 18 therein.

In one embodiment there is provided a variable region, such as a heavychain variable region with the following sequence (Antibody 923anti-toxin A antibody heavy chain variable region sequence) SEQ ID NO:19:

EVQLVESGGGLVQPGGSLRLSCAASAFSLSNYYMSWVRQAPGKGLEWIGIISSGSNALKWYASWPKGRFTISKDSTTVYLQMNSLRAEDTATYFCARNYV GSGSYYGMDLWGQGTLVTVSwherein the CDRs are underlined and construct is referred to herein asCA923.g1 gH1

The polynucleotide sequence encoding SEQ ID NO: 19 is shown in FIG. 2and SEQ ID NO: 20 therein.

In one embodiment an antibody according to the invention comprisesvariable regions shown in SEQ ID NO 17: and SEQ ID NO: 19.

In one embodiment there is provided an antibody (for example ananti-toxin A antibody) comprising a CDR, such as 1, 2, 3, 4, 5 or 6CDRs, selected from:

SEQ ID NO: 21 QASQSISSYFS SEQ ID NO: 22 GASTLAS SEQ ID NO: 23QCTDYSGIYFGG SEQ ID NO: 24 GFSLSSYYMS SEQ ID NO: 25 IISSGSSTTFTWYASWAKGSEQ ID NO: 26 AYVGSSSYYGFDP

In one embodiment sequences 21 to 23 are in a light chain of theantibody.

In one embodiment sequences 24 to 26 are in a heavy chain of theantibody.

In one embodiment SEQ ID NO: 21 is CDR L1, SEQ ID NO: 22 is CDR L2 andSEQ ID NO; 23 is CDR L3.

In one embodiment SEQ ID NO: 24 is CDR H1, SEQ ID NO: 25 is CDR H2 andSEQ ID NO; 26 is CDR H3.

In one embodiment SEQ ID NO: 21 is CDR L1, SEQ ID NO: 22 is CDR L2, SEQID NO; 23 is CDR L3, SEQ ID NO: 24 is CDR H1, SEQ ID NO: 25 is CDR H2and SEQ ID NO; 26 is CDR H3.

In one embodiment there is provided a variable region, such as a lightchain variable region with the following sequence (Antibody 993anti-toxin A antibody; Light chain Variable region sequence) SEQ ID NO:27:

DVVMTQSPSTLSASVGDRVTITCQASQSISSYFSWYQQKPGKAPQLLIYGASTLASGVPSRFKGSGSGTELTLTISSLQPDDFATYYCQCTDYSGIYFGG FGGGTKVEIKwherein the CDRs are underlined and construct is referred to herein asCA993.g1 gL1

The polynucleotide sequence encoding SEQ ID NO: 27 is shown in FIG. 2and SEQ ID NO: 28 therein.

In one embodiment there is provided a variable region, such as a heavychain variable region with the following sequence (Antibody 993anti-toxin A antibody heavy chain variable region sequence) SEQ ID NO:29:

EVQLVESGGGLVQPGGSLKLSCTASGFSLSSYYMSWVRQAPGKGLEWIGIISSGSSTTFTWYASWAKGRFTISKTSTTVYLQMNSLKTEDTATYFCARAY VGSSSYYGFDPWGQGTLVTVSwherein the CDRs are underlined and construct is referred to herein asCA993.g1 gH1

The polynucleotide sequence encoding SEQ ID NO: 29 is shown in FIG. 2and SEQ ID NO: 30 therein.

In one embodiment an antibody according to the invention comprisesvariable regions shown in SEQ ID NO: 27 and SEQ ID NO: 29.

In one embodiment there is provided an antibody (for example ananti-toxin A antibody) comprising a CDR, such as 1, 2, 3, 4, 5 or 6CDRs, selected from:

SEQ ID NO: 31 QASQSINNYFS SEQ ID NO: 32 GAANLAS SEQ ID NO: 33QNNYGVHIYGAA SEQ ID NO: 34 GFSLSNYDMI SEQ ID NO: 35 FINTGGITYYASWAKGSEQ ID NO: 36 VDDYIGAWGAGL

In one embodiment sequences 31 to 33 are in a light chain of theantibody.

In one embodiment sequences 34 to 36 are in a heavy chain of theantibody.

In one embodiment SEQ ID NO: 31 is CDR L1, SEQ ID NO: 32 is CDR L2 andSEQ ID NO; 33 is CDR L3.

In one embodiment SEQ ID NO: 34 is CDR H1, SEQ ID NO: 35 is CDR H2 andSEQ ID NO: 36 is CDR H3.

In one embodiment SEQ ID NO: 31 is CDR L1, SEQ ID NO: 32 is CDR L2, SEQID NO; 33 is CDR L3, SEQ ID NO: 34 is CDR H1, SEQ ID NO: 35 is CDR H2and SEQ ID NO; 36 is CDR H3.

In one embodiment there is provided a variable region, such as a lightchain variable region with the following sequence (Antibody 995anti-toxin A antibody; Light chain Variable region sequence) SEQ ID NO:37:

DVVMTQSPSTLSASVGDRVTITCQASQSINNYFSWYQQKPGKAPKLLIYGAANLASGVPSRFKGSGSGTEYTLTISSLQPDDFATYSCQNNYGVHIYGAA FGGGTKVEIKwherein the CDRs are underlined

The polynucleotide sequence encoding SEQ ID NO: 37 is shown in FIG. 3and SEQ ID NO: 38 therein.

In one embodiment there is provided a variable region, such as a heavychain variable region with the following sequence (Antibody 995anti-toxin A antibody heavy chain variable region sequence) SEQ ID NO:39

EVQLVESGGGLVQPGGSLRLSCTASGFSLSNYDMIWVRQAPGKGLEYIGFINTGGITYYASWAKGRFTISRDSSTVYLQMNSLRAEDTATYFCARVDDYI GAWGAGLWGQGTLVTVSwherein the CDRs are underlined

The polynucleotide sequence encoding SEQ ID NO: 39 is shown in FIG. 3and SEQ ID NO: 40 therein.

In one embodiment an antibody according to the invention comprisesvariable regions shown in SEQ ID NO: 37 and SEQ ID NO: 39.

In one embodiment there is provided an antibody (for example ananti-toxin A antibody) comprising a CDR, such as 1, 2, 3, 4, 5 or 6CDRs, selected from:

SEQ ID NO: 41 QASQSISSYLS SEQ ID NO: 42 RASTLAS SEQ ID NO: 43LGVYGYSNDDGIA SEQ ID NO: 44 GIDLSSHHMC SEQ ID NO: 45 VIYHFGSTYYANWATGSEQ ID NO: 46 ASIAGYSAFDP

In one embodiment sequences 41 to 43 are in a light chain of theantibody.

In one embodiment sequences 44 to 46 are in a heavy chain of theantibody.

In one embodiment SEQ ID NO: 41 is CDR L1, SEQ ID NO: 42 is CDR L2 andSEQ ID NO; 43 is CDR L3.

In one embodiment SEQ ID NO: 44 is CDR H1, SEQ ID NO: 45 is CDR H2 andSEQ ID NO: 46 is CDR H3.

In one embodiment SEQ ID NO: 41 is CDR L1, SEQ ID NO: 42 is CDR L2, SEQID NO; 43 is CDR L3, SEQ ID NO: 44 is CDR H1, SEQ ID NO: 45 is CDR H2and SEQ ID NO; 46 is CDR H3.

In one embodiment there is provided a variable region, such as a lightchain variable region with the following sequence (Antibody 997anti-toxin A antibody; Light chain Variable region sequence) SEQ ID NO:47:

ALVMTQSPSSFSASTGDRVTITCQASQSISSYLSWYQQKPGKAPKLLIYRASTLASGVPSRFSGSGSGTEYTLTISCLQSEDFATYYCLGVYGYSNDDGI AFGGGTKVEIKwherein the CDRs are underlined

The polynucleotide sequence encoding SEQ ID NO: 47 is shown in FIG. 3and SEQ ID NO: 48 therein.

In one embodiment there is provided a variable region, such as a heavychain variable region with the following sequence (Antibody 997anti-toxin A antibody heavy chain variable region sequence) SEQ ID NO:49:

EVQLVESGGGLVQPGGSLRLSCTVSGIDLSSHHMCWVRQAPGKGLEYIGVIYHFGSTYYANWATGRFTISKDSTTVYLQMNSLRAEDTATYFCARASIAG YSAFDPWGQGTLVTVSwherein the CDRs are underlined

The polynucleotide sequence encoding SEQ ID NO: 49 is shown in FIG. 4and SEQ ID NO: 50 therein.

In one embodiment an antibody according to the invention comprisesvariable regions shown in SEQ ID NO: 47 and SEQ ID NO: 49.

In one embodiment there is provided an antibody (for example ananti-toxin A antibody) comprising a CDR, such as 1, 2, 3, 4, 5 or 6CDRs, selected from:

SEQ ID NO: 51 QASQSIYSYLA SEQ ID NO: 52 DASTLAS SEQ ID NO: 53QGNAYTSNSHDNA SEQ ID NO: 54 GIDLSSDAVG SEQ ID NO: 55 IIATFDSTYYASWAKGSEQ ID NO: 56 TGSWYYISGWGSYYYGMDL

In one embodiment sequences 51 to 53 are in a light chain of theantibody.

In one embodiment sequences 54 to 56 are in a heavy chain of theantibody.

In one embodiment SEQ ID NO: 51 is CDR L1, SEQ ID NO: 52 is CDR L2 andSEQ ID NO: 53 is CDR L3.

In one embodiment SEQ ID NO: 54 is CDR H1, SEQ ID NO: 55 is CDR H2 andSEQ ID NO; 56 is CDR H3.

In one embodiment SEQ ID NO: 51 is CDR L1, SEQ ID NO: 52 is CDR L2, SEQID NO; 53 is CDR L3, SEQ ID NO: 54 is CDR H1, SEQ ID NO: 55 is CDR H2and SEQ ID NO: 56 is CDR H3.

In one embodiment there is provided a variable region, such as a lightchain variable region with the following sequence (Antibody 1000anti-toxin A antibody; Light chain Variable region sequence) SEQ ID NO:57:

EIVMTQSPSTLSASVGDRVTITCQASQSIYSYLAWYQQKPGKAPKLLIYDASTLASGVPSRFKGSGSGTEFTLTISSLQPDDFATYYCQGNAYTSNSHDN AFGGGTKVEIKwherein the CDRs are underlined.

The polynucleotide sequence encoding SEQ ID NO: 57 is shown in FIG. 4and SEQ ID NO: 58 therein.

In one embodiment there is provided a variable region, such as a heavychain variable region with the following sequence (Antibody 1000anti-toxin A antibody heavy chain variable region sequence) SEQ ID NO:59:

EVQLVESGGGLIQPGGSLRLSCTVSGIDLSSDAVGWVRQAPGKGLEYIGIIATFDSTYYASWAKGRFTISKASSTTVYLQMNSLRAEDTATYFCARTGSWYYISGWGSYYYGMDLWGQGTLVTVSwherein the CDRs are underlined.

The polynucleotide sequence encoding SEQ ID NO: 59 is shown in FIG. 4and SEQ ID NO: 60 therein.

In one embodiment an antibody according to the invention comprisesvariable regions shown in SEQ ID NO: 57 and SEQ ID NO: 59.

In one embodiment there is provided an antibody (for example ananti-toxin B antibody) comprising a CDR, such as 1, 2, 3, 4, 5 or 6CDRs, selected from:

SEQ ID NO: 61 RASKSVSTLMH SEQ ID NO: 62 LASNLES SEQ ID NO: 63 QQTWNDPWTSEQ ID NO: 64 GFTFSNYGMA SEQ ID NO: 65 SISSSGGSTYYRDSVKG SEQ ID NO: 66VIRGYVMDA

In one embodiment sequences 61 to 63 are in a light chain of theantibody.

In one embodiment sequences 64 to 66 are in a heavy chain of theantibody.

In one embodiment SEQ ID NO: 61 is CDR L1, SEQ ID NO: 62 is CDR L2 andSEQ ID NO: 63 is CDR L3.

In one embodiment SEQ ID NO: 64 is CDR H1, SEQ ID NO: 65 is CDR H2 andSEQ ID NO: 66 is CDR H3.

In one embodiment SEQ ID NO: 61 is CDR L1, SEQ ID NO: 62 is CDR L2, SEQID NO; 63 is CDR L3, SEQ ID NO: 64 is CDR H1, SEQ ID NO: 65 is CDR H2and SEQ ID NO: 66 is CDR H3.

In one embodiment there is provided a variable region, such as a lightchain variable region with the following sequence (Antibody 926anti-toxin B antibody; Light chain Variable region sequence) SEQ ID NO:67:

DTVLTQSPATLSLSPGERATLSCRASKSVSTLMHWFQQKPGQAPKLLIYLASNLESGVPARFSGSGSGTDFTLTISSLEPEDFAVYYCQQTWNDPWTFGG GTKVEIKwherein the CDRs are underlined.

The polynucleotide sequence encoding SEQ ID NO: 67 is shown in FIG. 5and SEQ ID NO: 68 therein.

In one embodiment there is provided a variable region, such as a heavychain variable region with the following sequence (Antibody 926anti-toxin B antibody heavy chain variable region sequence) SEQ ID NO:69:

EVELLESGGGLVQPGGSLRLSCEASGFTFSNYGMAWVRQAPTKGLEWVTSISSSGGSTYYRDSVKGRFTISRDNAKSSLYLQMNSLRAEDTATYYCTTVI RGYVMDAWGQGTLVTVSwherein the CDRs are underlined.

The polynucleotide sequence encoding SEQ ID NO: 69 is shown in FIG. 5and SEQ ID NO: 70 therein.

In one embodiment there is provided an antibody (for example ananti-toxin B antibody) comprising a CDR, such as 1, 2, 3, 4, 5 or 6CDRs, selected from:

SEQ ID NO: 71 RASGSVSTLMH SEQ ID NO: 72 KASNLAS SEQ ID NO: 73 HQSWNSDTSEQ ID NO: 74 GFTFSNYGMA SEQ ID NO: 75 TINYDGRTTHYRDSVKG SEQ ID NO: 76ISRSHYFDC

In one embodiment sequences 71 to 73 are in a light chain of theantibody.

In one embodiment sequences 74 to 76 are in a heavy chain of theantibody.

In one embodiment SEQ ID NO: 71 is CDR L1, SEQ ID NO: 72 is CDR L2 andSEQ ID NO: 73 is CDR L3.

In one embodiment SEQ ID NO: 74 is CDR H1, SEQ ID NO: 75 is CDR H2 andSEQ ID NO: 76 is CDR H3.

In one embodiment SEQ ID NO: 71 is CDR L1, SEQ ID NO: 72 is CDR L2, SEQID NO; 73 is CDR L3, SEQ ID NO: 74 is CDR H1, SEQ ID NO: 75 is CDR H2and SEQ ID NO: 76 is CDR H3.

In one embodiment there is provided a variable region, such as a lightchain variable region with the following sequence (Antibody 927anti-toxin B antibody; Light chain Variable region sequence) SEQ ID NO:77:

DTQMTQSPSTLSASVGDRVTITCRASGSVSTLMHWYQQKPGKAPKLLIYKASNLASGVPSRFSGSGSGTEFTLTISSLQPDDFATYYCHQSWNSDTFGQG TRLEIKwherein the CDRs are underlined

The polynucleotide sequence encoding SEQ ID NO: 77 is shown in FIG. 5and SEQ ID NO: 78 therein.

In one embodiment there is provided a variable region, such as a heavychain variable region with the following sequence (Antibody 927anti-toxin B antibody heavy chain variable region sequence) SEQ ID NO:79:

EVQLVESGGGVVQPGRSLRLSCAASGFTFSNYGMAWVRQAPGKGLEWVATINYDGRTTHYRDSVKGRFTISRDNSKSTLYLQMNSLRAEDTAVYYCTSIS RSHYFDCWGQGTLVTVSwherein the CDRs are underlined.

The polynucleotide sequence encoding SEQ ID NO: 79 is shown in FIG. 5and SEQ ID NO: 80 therein.

In one embodiment an antibody according to the invention comprisesvariable regions shown in SEQ ID NO: 77 and SEQ ID NO: 79.

In one embodiment there is provided an antibody (for example ananti-toxin B antibody) comprising a CDR, such as 1, 2, 3, 4, 5 or 6CDRs, selected from:

SEQ ID NO: 81 KASKSISNHLA SEQ ID NO: 82 SGSTLQS SEQ ID NO: 83 QQYDEYPYTSEQ ID NO: 84 GFSLQSYTIS SEQ ID NO: 85 AISGGGSTYYNLPLKS SEQ ID NO: 86PRWYPRSYFDY

In one embodiment sequences 81 to 83 are in a light chain of theantibody.

In one embodiment sequences 84 to 86 are in a heavy chain of theantibody.

In one embodiment SEQ ID NO: 81 is CDR L1, SEQ ID NO: 82 is CDR L2 andSEQ ID NO: 83 is CDR L3.

In one embodiment SEQ ID NO: 84 is CDR H1, SEQ ID NO: 85 is CDR H2 andSEQ ID NO: 86 is CDR H3.

In one embodiment SEQ ID NO: 81 is CDR L1, SEQ ID NO: 82 is CDR L2, SEQID NO; 83 is CDR L3, SEQ ID NO: 84 is CDR H1, SEQ ID NO: 85 is CDR H2and SEQ ID NO: 86 is CDR H3.

In one embodiment there is provided a variable region, such as a lightchain variable region with the following sequence (Antibody 1099anti-toxin B antibody; Light chain Variable region sequence) SEQ ID NO:87:

DVQLTQSPSFLSASVGDRVTITCKASKSISNHLAWYQEKPGKANKLLIHSGSTLQSGTPSRFSGSGSGTEFTLTISSLQPEDFATYYCQQYDEYPYTFGQ GTRLEIKRTwherein the CDRs are underlined.

In one embodiment the last two amino acids (RT) of SEQ ID NO: 87 areomitted.

The polynucleotide sequence encoding SEQ ID NO: 87 is shown in FIG. 6and SEQ ID NO: 88 therein. In one embodiment the codons encoding thelast two amino acids (RT) are omitted.

In one embodiment there is provided a variable region, such as a heavychain variable region with the following sequence (Antibody 1099anti-toxin B antibody heavy chain variable region sequence) SEQ ID NO:89:

EVQLQESGPGLVKPSETLSLTCTVSGFSLQSYTISWVRQPPGKGLEWIAAISGGGSTYYNLPLKSRVTISRDTSKSQVSLKLSSVTAADTAVYYCTRPRW YPRSYFDYWGRGTLVTVSwherein the CDRs are underlined

The polynucleotide sequence encoding SEQ ID NO: 89 is shown in FIG. 6and SEQ ID NO: 90 therein.

In one embodiment an antibody according to the invention comprisesvariable regions shown in SEQ ID NO 87: and SEQ ID NO: 89.

In one embodiment there is provided an antibody (for example ananti-toxin B antibody) comprising a CDR, such as 1, 2, 3, 4, 5 or 6CDRs, selected from:

SEQ ID NO: 91 RASQRISTSIH SEQ ID NO: 92 YASQSIS SEQ ID NO: 93 QQSYSSLYTSEQ ID NO: 94 GFTFSDSYMA SEQ ID NO: 95 SISYGGTIIQYGDSVKG SEQ ID NO: 96RQGTYARYLDF

In one embodiment sequences 91 to 93 are in a light chain of theantibody.

In one embodiment sequences 94 to 96 are in a heavy chain of theantibody.

In one embodiment SEQ ID NO: 91 is CDR L1, SEQ ID NO: 92 is CDR L2 andSEQ ID NO; 93 is CDR L3.

In one embodiment SEQ ID NO: 94 is CDR H1, SEQ ID NO: 95 is CDR H2 andSEQ ID NO: 96 is CDR H3.

In one embodiment SEQ ID NO: 91 is CDR L1, SEQ ID NO: 92 is CDR L2, SEQID NO; 93 is CDR L3, SEQ ID NO: 94 is CDR H1, SEQ ID NO: 95 is CDR H2and SEQ ID NO: 96 is CDR H3.

In one embodiment there is provided a variable region, such as a lightchain variable region with the following sequence (Antibody 1102anti-toxin B antibody; Light chain Variable region sequence) SEQ ID NO:97:

NIVLTQSPATLSLSPGERATLSCRASQRISTSIHWYQQKPGQAPRLLIKYASQSISGIPARFSGSGSGTDFTLTISSLEPEDFAVYYCQQSYSSLYTFGQ GTKLEIKwherein the CDRs are underlined

The polynucleotide sequence encoding SEQ ID NO: 97 is shown in FIG. 6and SEQ ID NO: 98 therein.

In one embodiment there is provided a variable region, such as a heavychain variable region with the following sequence (Antibody 1102anti-toxin B antibody heavy chain variable region sequence) SEQ ID NO:99:

EVQLVESGGGLVQPGGSLRLSCAVSGFTFSDSYMAWVRQAPGKGLEWIASISYGGTIIQYGDSVKGRFTISRDNAKSSLYLQMNSLRAEDTAVYYCARRQ GTYARYLDFWGQGTLVTVSwherein the CDRs are underlined.

The polynucleotide sequence encoding SEQ ID NO: 99 is shown in FIG. 7and SEQ ID NO: 100 therein.

In one embodiment an antibody according to the invention comprisesvariable regions shown in SEQ ID NO 97: and SEQ ID NO: 99.

In one embodiment there is provided an antibody (for example ananti-toxin B antibody) comprising a CDR, such as 1, 2, 3, 4, 5 or 6CDRs, selected from:

SEQ ID NO: 101 RASESVSTLLH SEQ ID NO: 102 KASNLAS SEQ ID NO: 103HQSWNSPPT SEQ ID NO: 104 GFTFSNYGMA SEQ ID NO: 105 IINYDASTTHYRDSVKGSEQ ID NO: 106 YGRSHYFDY

In one embodiment sequences 101 to 103 are in a light chain of theantibody.

In one embodiment sequences 104 to 106 are in a heavy chain of theantibody.

In one embodiment SEQ ID NO: 101 is CDR L1, SEQ ID NO: 102 is CDR L2 andSEQ ID NO: 103 is CDR L3.

In one embodiment SEQ ID NO: 104 is CDR H1, SEQ ID NO: 105 is CDR H2 andSEQ ID NO: 106 is CDR H3.

In one embodiment SEQ ID NO: 101 is CDR L1, SEQ ID NO: 102 is CDR L2,SEQ ID NO; 103 is CDR L3, SEQ ID NO: 104 is CDR H1, SEQ ID NO: 105 isCDR H2 and SEQ ID NO; 106 is CDR H3.

In one embodiment there is provided a variable region, such as a lightchain variable region with the following sequence (Antibody 1114anti-toxin B antibody; Light chain Variable region sequence) SEQ ID NO:107:

ATQMTQSPSSLSASVGDRVTITCRASESVSTLLHWYQQKPGKAPKLLIYKASNLASGVPSRFSGSGSGTDFTLTISSLQPEDFATYYCHQSWNSPPTFGQ GTKLEIKwherein the CDRs are underlined.

The polynucleotide sequence encoding SEQ ID NO: 107 is shown in FIG. 7and SEQ ID NO: 108 therein.

In one embodiment there is provided a variable region, such as a heavychain variable region with the following sequence (Antibody 1114anti-toxin B antibody heavy chain variable region sequence) SEQ ID NO:109:

EVQLVESGGGLVQPGGSLRLSCAASGFTFSNYGMAWVRQAPGKGLEWVAIINYDASTTHYRDSVKGRFTISRDNAKSSLYLQMNSLRAEDTAVYYCTRYG RSHYFDYWGQGTLVTVSwherein the CDRs are underlined.

The polynucleotide sequence encoding SEQ ID NO: 109 is shown in FIG. 7and SEQ ID NO: 110 therein.

In one embodiment an antibody according to the invention comprisesvariable regions shown in SEQ ID NO: 107 and SEQ ID NO: 109.

In one embodiment there is provided an antibody (for example ananti-toxin B antibody) comprising a CDR, such as 1, 2, 3, 4, 5 or 6CDRs, selected from:

SEQ ID NO: 111 RASESVSTLLH SEQ ID NO: 112 KASNLAS SEQ ID NO: 113HQSWNSPPT SEQ ID NO: 114 GFTFSNYGMA SEQ ID NO: 115 IINYDASTTHYRDSVKSEQ ID NO: 116 YGRSHYFDY

In one embodiment sequences 111 to 113 are in a light chain of theantibody.

In one embodiment sequences 114 to 116 are in a heavy chain of theantibody.

In one embodiment SEQ ID NO: 111 is CDR L1, SEQ ID NO: 112 is CDR L2 andSEQ ID NO: 113 is CDR L3.

In one embodiment SEQ ID NO: 114 is CDR H1, SEQ ID NO: 115 is CDR H2 andSEQ ID NO: 116 is CDR H3.

In one embodiment SEQ ID NO: 111 is CDR L1, SEQ ID NO: 112 is CDR L2,SEQ ID NO; 113 is CDR L3, SEQ ID NO: 114 is CDR H1, SEQ ID NO: 115 isCDR H2 and SEQ ID NO: 116 is CDR H3.

In one embodiment there is provided a variable region, such as a lightchain variable region with the following sequence (Antibody 1114 graft 8anti-toxin B antibody; Light chain Variable region sequence) SEQ ID NO:117:

DTVLTQSPSSLSASVGDRVTITCRASESVSTLLHWYQQKPGKAPKLLIYKASNLASGVPSRFSGSGSGTDFTLTISSLQPEDFATYYCHQSWNSPPTFGQ GTKLEIKwherein the CDRs are underlined.

The polynucleotide sequence encoding SEQ ID NO: 117 is shown in FIG. 8and SEQ ID NO: 118 therein.

In one embodiment there is provided a variable region, such as a heavychain variable region with the following sequence (Antibody 1114 graft 8anti-toxin B antibody heavy chain variable region sequence) SEQ ID NO:119:

EVQLVESGGGLVQPGGSLRLSCAASGFTFSNYGMAWVRQAPGKGLEWVAIINYDASTTHYRDSVKGRFTISRDNAKSSLYLQMNSLRAEDTAVYYCTRYG RSHYFDYWGQGTLVTVSwherein the CDRs are underlined.

The polynucleotide sequence encoding SEQ ID NO: 119 is shown in FIG. 8and SEQ ID NO: 120 therein.

In one embodiment an antibody according to the invention comprisesvariable regions shown in SEQ ID NO: 117 and SEQ ID NO: 119.

In one embodiment there is provided an antibody (for example ananti-toxin B antibody) comprising a CDR, such as 1, 2, 3, 4, 5 or 6CDRs, selected from:

SEQ ID NO: 121 KASQNIYMYLN SEQ ID NO: 122 NTNKLHT SEQ ID NO: 123LQHKSFPYT SEQ ID NO: 124 GFTFRDSFMA SEQ ID NO: 125 SISYEGDKTYYGDSVKGSEQ ID NO: 126 LTITTSGDS

In one embodiment sequences 121 to 123 are in a light chain of theantibody.

In one embodiment sequences 124 to 126 are in a heavy chain of theantibody.

In one embodiment SEQ ID NO: 121 is CDR L1, SEQ ID NO: 122 is CDR L2 andSEQ ID NO: 123 is CDR L3.

In one embodiment SEQ ID NO: 124 is CDR H1, SEQ ID NO: 125 is CDR H2 andSEQ ID NO: 126 is CDR H3.

In one embodiment SEQ ID NO: 121 is CDR L1, SEQ ID NO: 122 is CDR L2,SEQ ID NO: 123 is CDR L3, SEQ ID NO: 124 is CDR H1, SEQ ID NO: 125 isCDR H2 and SEQ ID NO: 126 is CDR H3.

In one embodiment there is provided a variable region, such as a lightchain variable region with the following sequence (Antibody 1125anti-toxin B antibody; Light chain Variable region sequence) SEQ ID NO:127:

DIQMTQSPSSLSASVGDRVTITCKASQNIYMYLNWYQQKPGKAPKRLIYNTNKLHTGVPSRFSGSGSGTEYTLTISSLQPEDFATYYCLQHKSFPYTFGQ GTKLEIKwherein the CDRs are underlined.

The polynucleotide sequence encoding SEQ ID NO: 127 is shown in FIG. 8and SEQ ID NO: 128 therein.

In one embodiment there is provided a variable region, such as a heavychain variable region with the following sequence (Antibody 1125anti-toxin B antibody heavy chain variable region sequence) SEQ ID NO:129:

EVQLVESGGGLVQPGGSLRLSCAASGFTFRDSFMAWVRQAPGKGLEWVASISYEGDKTYYGDSVKGRFTISRDNAKNSLYLQMNSLRAEDTAVYYCARLT ITTSGDSWGQGTMVTVSSwherein the CDRs are underlined.

In one embodiment the last amino acid (S) of SEQ ID NO: 129 is omitted.

The polynucleotide sequence encoding SEQ ID NO: 129 is shown in FIG. 9and SEQ ID NO: 130 therein. In one embodiment the codon AGC encoding thelast amino acid S is omitted.

In one embodiment an antibody according to the invention comprisesvariable regions shown in SEQ ID NO: 127 and SEQ ID NO: 129.

In one embodiment there is provided antibody (for example an anti-toxinB antibody) comprising a CDR, such as 1, 2, 3, 4, 5 or 6 CDRs, selectedfrom:

SEQ ID NO: 131 KASQHVGTNVD SEQ ID NO: 132 GASIRYT SEQ ID NO: 133LQYNYNPYT SEQ ID NO: 134 GFIFSNFGMS SEQ ID NO: 135 SISPSGGNAYYRDSVKGSEQ ID NO: 136 RAYSSPFAF

In one embodiment sequences 131 to 133 are in a light chain of theantibody.

In one embodiment sequences 134 to 136 are in a heavy chain of theantibody.

In one embodiment SEQ ID NO: 131 is CDR L1, SEQ ID NO: 132 is CDR L2 andSEQ ID NO: 133 is CDR L3.

In one embodiment SEQ ID NO: 134 is CDR H1, SEQ ID NO: 135 is CDR H2 andSEQ ID NO: 136 is CDR H3.

In one embodiment SEQ ID NO: 131 is CDR L1, SEQ ID NO: 132 is CDR L2,SEQ ID NO: 133 is CDR L3, SEQ ID NO: 134 is CDR H1, SEQ ID NO: 135 isCDR H2 and SEQ ID NO: 136 is CDR H3.

In one embodiment there is provided a variable region, such as a lightchain variable region with the following sequence (Antibody 1129anti-toxin B antibody; Light chain Variable region sequence) SEQ ID NO:137:

DTQMTQSPSSLSASVGDRVTITCKASQHVGTNVDWYQQKPGKVPKLLIYGASIRYTGVPDRFTGSGSGTDFTLTISSLQPEDVATYYCLQYNYNPYTFGQ GTKLEIKwherein the CDRs are underlined.

The polynucleotide sequence encoding SEQ ID NO: 137 is shown in FIG. 8and SEQ ID NO: 138 therein.

In one embodiment there is provided a variable region, such as a heavychain variable region with the following sequence (Antibody 1129anti-toxin B antibody heavy chain variable region sequence) SEQ ID NO:139:

EVQLVESGGGVVQPGRSLRLSCATSGFIFSNFGMSWVRQAPGKGLEWVASISPSGGNAYYRDSVKGRFTISRDNSKTTLYLQMNSLRAEDTAVYYCTRRA YSSPFAFWGQGTLVTVSSwherein the CDRs are underlined.

In one embodiment the last amino acid (S) of SEQ ID NO: 139 is omitted.

The polynucleotide sequence encoding SEQ ID NO: 139 is shown in FIG. 8and SEQ ID NO: 140 therein. In one embodiment the codon AGC encoding thelast amino acid S is omitted.

In one embodiment an antibody according to the invention comprisesvariable regions shown in SEQ ID NO: 137 and SEQ ID NO: 139.

In one embodiment there is provided an antibody (for example ananti-toxin B antibody) comprising a CDR, such as 1, 2, 3, 4, 5 or 6CDRs, selected from:

SEQ ID NO: 141 KASKSISNHLA SEQ ID NO: 142 SGSTLQP SEQ ID NO: 143QQYDEYPYT SEQ ID NO: 144 GFSLNSYTIT SEQ ID NO: 145 AISGGGSTYFNSALKSSEQ ID NO: 146 PRWYPRSYFDY

In one embodiment sequences 141 to 143 are in a light chain of theantibody.

In one embodiment sequences 144 to 146 are in a heavy chain of theantibody.

In one embodiment SEQ ID NO: 141 is CDR L1, SEQ ID NO: 142 is CDR L2 andSEQ ID NO: 143 is CDR L3.

In one embodiment SEQ ID NO: 144 is CDR H1, SEQ ID NO: 145 is CDR H2 andSEQ ID NO: 146 is CDR H3.

In one embodiment SEQ ID NO: 141 is CDR L1, SEQ ID NO: 142 is CDR L2,SEQ ID NO: 143 is CDR L3, SEQ ID NO: 144 is CDR H1, SEQ ID NO: 145 isCDR H2 and SEQ ID NO: 146 is CDR H3.

In one embodiment there is provided a variable region, such as a lightchain variable region with the following sequence (Antibody 1134anti-toxin B antibody; Light chain Variable region sequence):

SEQ ID NO: 147 DVQLTQSPSFLSASVGDRVTITCKASKSISNHLAWYQEKPGKANKLLIHSGSTLQPGTPSRFSGSGSGTEFTLTISSLQPEDFATYYCQQYDEYPYTF GQGTRLEIKwherein the CDRs are underlined.

The polynucleotide sequence encoding SEQ ID NO: 147 is shown in FIG. 9and SEQ ID NO: 148 therein.

In one embodiment there is provided a variable region, such as a heavychain variable region with the following sequence (Antibody 1134anti-toxin B antibody heavy chain variable region sequence) SEQ ID NO:149:

EVQLQESGPGLVKPSETLSLTCTVSGFSLNSYTITWVRQPPGKGLEWIAAISGGGSTYFNSALKSRVTISRDTSKSQVSLKLSSVTAADTAVYYCTRP RWYPRSYFDYWGRGTLVTVSwherein the CDRs are underlined

The polynucleotide sequence encoding SEQ ID NO: 149 is shown in FIG. 9and SEQ ID NO: 150 therein.

In one embodiment an antibody according to the invention comprisesvariable regions shown in SEQ ID NO 147: and SEQ ID NO: 149.

In one embodiment there is provided antibody (for example an anti-toxinB antibody) comprising a CDR, such as 1, 2, 3, 4, 5 or 6 CDRs, selectedfrom:

SEQ ID NO: 151 KASQNVGNNVA SEQ ID NO: 152 YASNRFT SEQ ID NO: 153QRVYQSTWT SEQ ID NO: 154 GFSLTSYYVH SEQ ID NO: 155 CIRTGGNTEYQSEFKSSEQ ID NO: 156 GNYGFAY

In one embodiment sequences 151 to 153 are in a light chain of theantibody.

In one embodiment sequences 154 to 156 are in a heavy chain of theantibody.

In one embodiment SEQ ID NO: 151 is CDR L1, SEQ ID NO: 152 is CDR L2 andSEQ ID NO: 153 is CDR L3.

In one embodiment SEQ ID NO: 154 is CDR H1, SEQ ID NO: 155 is CDR H2 andSEQ ID NO: 156 is CDR H3.

In one embodiment SEQ ID NO: 151 is CDR L1, SEQ ID NO: 152 is CDR L2,SEQ ID NO; 153 is CDR L3, SEQ ID NO: 154 is CDR H1, SEQ ID NO: 155 isCDR H2 and SEQ ID NO; 156 is CDR H3.

In one embodiment there is provided a variable region, such as a lightchain variable region with the following sequence (Antibody 1151anti-toxin B antibody; Light chain Variable region sequence) SEQ ID NO:157:

AIQMTQSPSSLSASVGDRVTITCKASQNVGNNVAWYQHKPGKAPKLLIYYASNRFTGVPSRFTGGGYGTDFTLTISSLQPEDFATYYCQRVYQSTWTF GQGTKVEIKwherein the CDRs are underlined.

The polynucleotide sequence encoding SEQ ID NO: 157 is shown in FIG. 9and SEQ ID NO: 158 therein.

In one embodiment there is provided a variable region, such as a heavychain variable region with the following sequence (Antibody 1151anti-toxin B antibody heavy chain variable region sequence) SEQ ID NO:159:

EVQLQESGPGLVKPSETLSLTCTVSGFSLTSYYVHWVRQPPGKGLEWMGCIRTGGNTEYQSEFKSRVTISRDTSKNQVSLKLSSVTAADTAVYYCARG NYGFAYWGQGTLVTVSwherein the CDRs are underlined.

The polynucleotide sequence encoding SEQ ID NO: 159 is shown in FIG. 9and SEQ ID NO: 160 therein.

In one embodiment an antibody according to the invention comprisesvariable regions shown in SEQ ID NO: 157 and SEQ ID NO: 159.

In one embodiment there is provided an antibody (for example ananti-toxin B antibody) comprising a CDR, such as 1, 2, 3, 4, 5 or 6CDRs, selected from:

SEQ ID NO: 161 KASQNINKYLD SEQ ID NO: 162 NIQSLHT SEQ ID NO: 163 FQHNSGWSEQ ID NO: 164 GFTFTQAAMF SEQ ID NO: 165 RISTKSNNFATYYPDSVKGSEQ ID NO: 166 PAYYYDGTVPFAY

In one embodiment sequences 161 to 163 are in a light chain of theantibody.

In one embodiment sequences 164 to 166 are in a heavy chain of theantibody.

In one embodiment SEQ ID NO: 161 is CDR L1, SEQ ID NO: 162 is CDR L2 andSEQ ID NO: 163 is CDR L3.

In one embodiment SEQ ID NO: 164 is CDR H1, SEQ ID NO: 165 is CDR H2 andSEQ ID NO: 166 is CDR H3.

In one embodiment SEQ ID NO: 161 is CDR L1, SEQ ID NO: 162 is CDR L2,SEQ ID NO: 163 is CDR L3, SEQ ID NO: 164 is CDR H1, SEQ ID NO: 165 isCDR H2 and SEQ ID NO: 166 is CDR H3.

In one embodiment there is provided a variable region, such as a lightchain variable region with the following sequence (Antibody 1153anti-toxin B antibody; Light chain Variable region sequence) SEQ ID NO:167:

DIQMTQSPSSLSASVGDRVTITCKASQNINKYLDWYQQKPGKVPKLLIYNIQSLHTGIPSRFSGSGSGTDFTLTISSLQPEDVATYYCFQHNSGWTFG QGTRLEIKwherein the CDRs are underlined.

The polynucleotide sequence encoding SEQ ID NO: 167 is shown in FIG. 10and SEQ ID NO: 168 therein.

In one embodiment there is provided a variable region, such as a heavychain variable region with the following sequence (Antibody 1153anti-toxin B antibody heavy chain variable region sequence) SEQ ID NO:169:

EVQLVESGGGLVQPGGSLKLSCAASGFTFTQAAMFWVRQASGKGLEGIARISTKSNNFATYYPDSVKGRFTISRDDSKNTVYLQMNSLKTEDTAVYYCTAPAYYYDGTVPFAYWGQGTLVTVSwherein the CDRs are underlined.

The polynucleotide sequence encoding SEQ ID NO: 169 is shown in FIG. 10and SEQ ID NO: 170 therein.

In one embodiment an antibody according to the invention comprisesvariable regions shown in SEQ ID NO: 167 and SEQ ID NO: 169.

In one embodiment there is provided antibody comprising 6 CDRsindependently selected from SEQ ID NOs 1, 2, 3, 4, 5, 6, 11, 12, 13, 14,15, 16, 21, 22, 23, 24, 25, 26, 31, 32, 33, 34, 35, 36, 41, 42, 43, 44,45, 46, 51, 52, 53, 54, 55, 56, 61, 62, 63, 64, 65, 66, 71, 72, 73, 74,75, 76, 81, 82, 83, 84, 85, 86, 91, 92, 93, 94, 95, 96, 101, 102, 103,104, 105, 106, 111, 112, 113, 114, 115, 116, 121, 122, 123, 124, 125,126, 131, 132, 133, 134, 135, 136, 141, 142, 143, 144, 145, 146, 151,152, 153, 154, 155, 156, 161, 162, 163, 164, 165 and 166.

In one embodiment there is provided an anti-TcdA antibody comprising 6CDRs independently selected from SEQ ID NOs 1, 2, 3, 4, 5, 6, 11, 12,13, 14, 15, 16, 21, 22, 23, 24, 25, 26, 31, 32, 33, 34, 35, 36, 41, 42,43, 44, 45, 46, 51, 52, 53, 54, 55 and 56.

In one embodiment there is provided an anti-TcdB antibody comprising 6CDRs independently selected from SEQ ID NOs 61, 62, 63, 64, 65, 66, 71,72, 73, 74, 75, 76, 81, 82, 83, 84, 85, 86, 91, 92, 93, 94, 95, 96, 101,102, 103, 104, 105, 106, 111, 112, 113, 114, 115, 116, 121, 122, 123,124, 125, 126, 131, 132, 133, 134, 135, 136, 141, 142, 143, 144, 145,146, 151, 152, 153, 154, 155, 156, 161, 162, 163, 164, 165 and 166.

In one embodiment there is provided an antibody which comprises twovariable regions independently selected from SEQ ID NOs: 7, 9, 17, 19,27, 29, 37, 39, 47, 49, 57, 59, 67, 69, 77, 79, 87, 89, 97, 99, 107,109, 117, 119, 127, 129, 137, 139, 147, 149, 157 and 159.

In one embodiment there is provided an antibody which comprises twovariable regions independently selected from SEQ ID NOs: 7, 9, 17, 19,27, 29, 37, 39, 47, 49, 57 and 59.

In one embodiment there is provided an antibody which comprises twovariable regions independently selected from SEQ ID NOs: 67, 69, 77, 79,87, 89, 97, 99, 107, 109, 117, 119, 127, 129, 137, 139, 147, 149, 157and 159.

In one embodiment the antibodies according to the invention arehumanized.

In one embodiment the antibody or antibodies are directed to the Cterminal “cell binding” portion of the TcdA and/or TcdB toxin.

In one embodiment an antibody according to the invention is suitable forneutralising toxin A or toxin B.

Neutralising as employed herein is intended to refer to the eliminationor reduction of harmful/deleterious effects of the target toxin, forexample at least a 50% reduction in the relevant harmful effect.

The inventors have established by using internal comparisons betweenantibodies discovered in this application and by comparison againstantibodies well described in the art (Babcock et al. 2006; Lowy et al.,2010) that some antibodies have the desirable characteristic ofmaintaining effective neutralization (for example low EC₅₀ and high %protection) even at high toxin concentrations. Other antibodiesincluding those described in the art do not maintain effective toxinneutralization at high toxin concentrations.

Effective toxin concentrations can be defined as a ‘lethal dose’ (LD) intitration studies in the absence of neutralizing antibodies.Neutralisation assays are typically conducted at an LD of 50% ofcomplete cell killing (i.e. an LD₅₀) but may be more rigorouslyconducted at an LD₅₀.

Assays may also be performed under considerably more challengingconditions such as LD₉₀, LD₉₅ and/or LD_(max) (LD_(max) is the maximaltoxin quantity which can be included in an assay as constrained by assayvolume and maximum toxin concentration/solubility). Such assays aim tomimic the early stages of infection of humans when C. difficile growthin the bowel is rampant and diarrhea and other symptoms lead one tohypothesise that toxin concentrations are at their highest. Antibodieswhich effectively neutralize damaging toxin activities under high toxinconcentration conditions are thought by the present inventors to havespecial clinical value for the control of symptoms in human infections.In one embodiment the antibody or antibodies of the present disclosurehave useful, for example low EC₅₀ values and/or high % protection fromcell death for one or more the LD₈₀, LD₉₀, LD₉₅ and/or LD_(max). In oneembodiment the EC₅₀ in the one or more of the latter situations is 15ng/ml or less, for example 10 ng/ml or less, such as 5 ng/ml or less, inparticular 1 ng/ml or less. In one embodiment the % protection from celldeath is >90%, or >75% or >50%.

Thus in one embodiment the present disclosure provides an antibody or acombination of antibodies which maintain toxin neutralization even inthe presence of high levels of toxin, for example as measured in anassay provided herein.

The harmful effect of toxin may, for example be measured in a suitablein vitro assay. In one embodiment the neutralization is measured in anassay given in Example 1 below. Also provided is an antibody orantibodies identified in a neutralization assay, for example wherein thepotency of the antibody is maintained in the presence of high levels oftoxin.

Toxin A is used interchangeably with TcdA.

Toxin B is used interchangeably with TcdB.

In one embodiment an antibody according to the invention is a monoclonalantibody or binding fragment thereof.

In one embodiment a monoclonal antibody according to the invention iscapable of neutralising TcdA with very high potency and affinity.

In one embodiment a monoclonal antibody according to the invention iscapable of neutralising TcdA with very high potency and affinity andhigh avidity.

Avidity as employed herein refers to the combined strength of multiplebinding affinities.

In one embodiment a monoclonal antibody according to the invention iscapable of neutralising TcdA with very high potency and affinity andhigh avidity and high valency of binding.

Valency of binding as employed herein refers to the ability for amonoclonal antibody to bind to an antigen multiple times. High valencyof binding hence results in high levels of decoration of antigen withantibodies and/or high levels of cross-linking of toxin molecules, whichis thought to be advantageous.

Anti-TcdA Mabs according to the present disclosure may be suitable forneutralising the early effects of TcdA, for example on cells such asloss of tight junctions.

Tight junction as employed herein is intended to refer to impermeablezone of connection between cells within a monolayer or anatomical tissuestructure. Fluid loss does not occur when tight junctions retain theirstructural and functional integrity. Loss of tight junctions is anindication that the cell has been compromised by toxin and is welldocumented as being an early step in the toxic effects of TcdA and TcdB(25) and results in loss of fluid containing serum, immunoglobulin andions (26, 3). Loss of tight junctions is thought to be a first step onthe onset of diarrhoea in humans.

The TEER assay system, can be used to measure the loss of tight junctionin vitro. TEER is an acronym for trans epithelial electric resistanceassay and it is generally employed to measure the permeability of adifferentiated cell layer representative of a gut endothelial lining.However, in the context of screening for antibodies TEER loss can beemployed to identify antibodies that slow or prevent damage to the tightjunctions and hence is a surrogate for protection against tissue damageleading to diarrhoea.

Often Caco-2 cells are employed since they are derived from human coloncells and are known to form differentiated monolayers with cellsconnected by tight junctions. A kit is commercially available fromBecton-Dickinson named the Caco-2 BioCoat HTS plate system (BDBiosciences/354802). The instructions in the kit are suitable fortesting in the present context. The resistance of the membrane changeswhen the membrane has been compromised.

Generally the antibody will be pre-incubated with the toxin beforeaddition to the TEER system to establish if the antibody can prevent orslow the damage to the membrane caused by the toxin. The assay may beperformed over a suitable period, for example 24 hours takingmeasurements at certain time-points. The present inventors haveestablished that the 4 hour time point is particularly discriminatingfor therapeutically useful antibodies. The concentration of toxinemployed in the TEER assay is generally in the range 100-200 ng/ml, mostpreferably 125 ng/ml

The concentration of antibody (for example IgG1) employed in the TEERassay is generally in the range of 4 to 2000 ng/ml, for example 50 to1000 ng/ml, such as 100 to 500 ng/ml.

In one embodiment the EC₅₀ of the antibody in the TEER assay employed insaid condition is at least 200 ng/ml, for example less than 100 ng/ml,such as about 60-80 ng/ml.

In one embodiment there is provided an anti-TcdA antibody or ananti-TcdB antibody suitable for use as a therapeutic agent in thetreatment or prevention of C. difficile infection, wherein said antibodywas screened and selected employing a TEER assay.

In one aspect there is provided a method of screening an antibody in aTEER assay for the ability to slow or prevent loss of tight junctions.In one embodiment the antibody or antibodies screened are anti-TcdAantibodies. In one embodiment the antibody or antibodies screened areanti-TcdB antibodies. In one embodiment the antibody or antibodiesscreened are a combination of anti-TcdA and anti-TcdB antibodies. In oneembodiment the method comprises the step of identifying an appropriateantibody or antibodies and expressing suitable quantities of same. Inone embodiment the method comprises the further step of formulating saidantibody or antibodies in a pharmaceutical formulation. In oneembodiment the method comprises the further step of administering saidantibody or antibodies or said formulation to a patient in need thereof.

In one embodiment multiple antibodies of the disclosure may be capableof binding to the target toxin (TcdA or TcdB), which may aid immuneclearance of the toxin.

Multiple antibodies as employed herein is intended to refer to multiplecopies of an antibody with the same sequence or an antibody with thesame amino acid sequence or an antibody specific to the same targetantigen but with a different amino acid sequence.

In one embodiment the antibodies according to the invention are specificto the target antigen, for example specific to an epitope in the targetantigen.

In one embodiment the antibodies of the invention are able to bind tothe target antigen in two or more locations, for example two or threelocations, such as four, five, six, seven, eight, nine, ten or morelocations, for example the toxin may comprise repeating domains and thusan antibody may be specific to an epitope and in fact that epitope maybe present in the antigen several times i.e. in more than one location.Thus given antibodies may bind the same epitope multiple times indifferent locations in the antigen.

In one embodiment the antibody binds to the given antigen multipletimes, for example 2 to 20 times such as 3, 4, 5, 6, 7, 8, 9, 10, 11,12, 13, 14, 15 or 16 times. In one embodiment the antibody binds thegiven antigen at least 3 times. This multiple binding is thought to beimportant in neutralisation and/or clearance of the toxin. Whilst notwishing to be bound by theory it is thought that multiple binding, forexample 3 more times, i.e. by decoration with 3 or more Fc fragments isimportant in triggering rapid clearance of the toxin (24) primarily viathe liver and spleen (27, 28).

In one embodiment the anti-TcdA antibody binds 3 or more times, forexample 3 to 16 times.

In one embodiment the anti-TcdA antibody binds 12 times.

In one embodiment the anti-TcdA antibody binds 2 times.

In one embodiment an anti-TcdA antibody binds in the catalytic-terminalcell binding domain of TcdA.

In one embodiment the anti-TcdB antibody binds 2 or more times, forexample 2 times.

In one embodiment an anti-TcdB antibody binds in the catalytic-terminalcell binding domain of TcdB.

In one embodiment the antibody or antibodies according to disclosure arecapable of cross-linking toxin molecules, for example one arm of theantibody molecule binds one toxin molecule and another of the antibodybinds a epitope in a different toxin molecule, thereby forming a sort ofimmune complex. The formation of the latter may also facilitateactivation of the immune system to clear the relate toxin and therebyminimise the deleterious in vivo effects of the same.

In one embodiment an innate immune response, such as complement isactivated.

In one embodiment the antibody or antibodies of the disclosure have highpotency against toxins derived from strains of different ribotypes, forexample 003, 027, 078.

In one embodiment antibodies against TcdA may have an EC₅₀ in the rangeof 0.1-100 ng/ml, such as 1 to 10 ng/ml and a maximal inhibition in therange of 50-100% at toxin concentrations of LD₈₀₋₉₅, for example againsttoxins from strains of ribotypes 003, 027 and 078.

In one embodiment antibodies against TcdA may have an EC₅₀ in the rangeof 0.1 100 ng/ml, such as 1 to 10 ng/ml and a maximal inhibition in therange of 60-100%, 70-100%, 80-100% or 90-100% at toxin concentrations ofLD₈₀₋₉₅, for example against toxins from strains of ribotypes 003, 027and 078.

In one embodiment antibodies against TcdB may have EC₅₀ in the range of0.1-100 ng/ml, such as 1 to 10 ng/ml and a maximal inhibition in therange of 50-100% at toxin concentrations of LD₈₀₋₉₅, for example againsttoxins from strains of ribotype 003.

In one embodiment antibodies against TcdB may have EC₅₀ in the range of0.1-100 ng/ml, such as 1 to 10 ng/ml and a maximal inhibition in therange of 60-100%, 70-100%, 80-100% or 90-100% at toxin concentrations ofLD₈₀₋₉₅, for example against toxins from strains of ribotype 003.

In one embodiment there are provided combinations of antibodiesaccording to the invention, for example combinations of antibodiesspecific to TcdA, combinations of antibodies specific to TcdB orcombinations of antibodies to specific to TcdA and antibodies specificto TcdB.

Combinations of antibodies specific to TcdA will generally refer tocombinations of antibodies directed to different epitopes on the targetantigen TcdA, or at least with different binding properties.

Combinations of antibodies specific to TcdB will generally refer tocombinations of antibodies directed to different epitopes on the targetantigen TcdB, or at least with different binding properties.

The combinations may comprise 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14or 15 distinct antibodies, for example 2, 3, 4 or 5 antibodies.

In one embodiment there is provided a combination of one anti-TcdAantibody and two anti-TcdB, for example wherein the anti-TcdA antibodyis 997 and where the anti-TcdB antibodies are 1125 and 1151

In particular there is provided a combination of one anti-TcdA antibodycomprising a heavy variable region with a sequence as shown in SEQ IDNO:49 and a light variable region with a sequence shown in SEQ ID NO: 47and two anti-TcdB antibodies the first with a heavy variable regionshown in SEQ ID NO: 129 and a light variable region shown in SEQ ID NO:127, and the second with a heavy variable region shown in SEQ ID NO: 159and light variable region shown in SEQ ID NO: 157.

Distinct antibodies as employed herein is intended to refer toantibodies with different amino acid sequences, which may bind the sameepitope or different epitopes on the target antigen.

Also provided by the present invention is a specific region or epitopeof TcdA which is bound by an antibody provided by the present invention,in particular an antibody comprising the heavy chain sequence given inSEQ ID NO:49 and the light chain sequence given in SEQ ID NO:47.

Also provided by the present invention is a specific region or epitopeof TcdB which is bound by an antibody provided by the present invention,in particular an antibody comprising the heavy chain sequence given inSEQ ID NO:129 and the light chain sequence given in SEQ ID NO:127 or anantibody comprising the heavy chain sequence given in SEQ ID NO:159 andthe light chain sequence given in SEQ ID NO:157.

This specific region or epitope of the TcdA or TcdB toxins can beidentified by any suitable epitope mapping method known in the art incombination with any one of the antibodies provided by the presentinvention. Examples of such methods include screening peptides ofvarying lengths derived from the toxins for binding to the antibody ofthe present invention with the smallest fragment that can specificallybind to the antibody containing the sequence of the epitope recognisedby the antibody. The peptides may be produced synthetically or byproteolytic digestion of the toxin polypeptide. Peptides that bind theantibody can be identified by, for example, mass spectrometric analysis.In another example, NMR spectroscopy or X-ray crystallography can beused to identify the epitope bound by an antibody of the presentinvention. Once identified, the epitopic fragment which binds anantibody of the present invention can be used, if required, as animmunogen to obtain additional antagonistic antibodies which bind thesame epitope.

Antibodies which cross-block the binding of an antibody according to thepresent invention may be similarly useful in neutralizing toxinactivity. Accordingly, the present invention also provides aneutralizing antibody having specificity for TcdA or TcdB, whichcross-blocks the binding of any one of the antibodies described above toTcdA or TcdB and/or is cross-blocked from binding these toxins by anyone of those antibodies. In one embodiment, such an antibody binds tothe same epitope as an antibody described herein above. In anotherembodiment the cross-blocking neutralising antibody binds to an epitopewhich borders and/or overlaps with the epitope bound by an antibodydescribed herein above. In another embodiment the cross-blockingneutralising antibody of this aspect of the invention does not bind tothe same epitope as an antibody of the present invention or an epitopethat borders and/or overlaps with said epitope.

Cross-blocking antibodies can be identified using any suitable method inthe art, for example by using competition ELISA or BIAcore assays wherebinding of the cross blocking antibody to TcdA or TcdB prevents thebinding of an antibody of the present invention or vice versa.

In one embodiment there is provided a method of generating an anti-TcdAor anti-TcdB antibody, in particular a neutralizing antibody and/or anantibody which cross-blocks the binding of an antibody described herein,said method comprising the steps of immunizing a host with a suitableantigen, for example an antigen shown in any one of SEQ ID Nos 173 to194 or a combination thereof. The said method may also comprise one ormore the following steps, for example identifying an antibody ofinterest (in particular using a functional assay such as TEER assay),expressing the antibody of interest, and optionally formulating theantibody as a pharmaceutically acceptable composition.

Thus in one aspect the present disclosure provides a method ofimmunizing a host with an amino acid sequence shown in SEQ ID Nos 173 to194 or a combination thereof.

In one embodiment the antibodies according to the invention have anaffinity to the target antigen of 10 nM or less, for example 1 nM orless such as 900 pM, in particular 800 pM, 700 pM, 600 pM or 500 pM,such as 60 pM.

In one embodiment the affinity is for TcdA or TcdB or a fragmentthereof. In one example the fragment is TcdA123 corresponding toresidues S1827-D2249 of TcdA. In one example the fragment is TcdA456corresponding to residues G2205-R2608. In one embodiment the fragment isTcdB1234 corresponding to residues S1833-E2366 of TcdB.

In one embodiment antibodies according to the invention or a combinationthereof have an EC₅₀ of 200 ng/ml or less, for example 150 ng/ml or lesssuch as 100 ng/ml or less, such as in the range 0.1 to 10 ng/ml.

The individual component antibodies of mixtures are not required to havean EC₅₀ in said range provided that when they are used in combinationwith one or more antibodies the combination has an EC₅₀ in said range.

Advantageously, the antibodies of the invention are stable, for exampleare thermally stable at temperatures above 50° C. such as 60 or 70° C.

The antibodies and combinations according to the present invention alsohave one or more of the following advantageous properties: slow offrate, high affinity, high potency, the ability to bind multiple times tothe target antigen, to neutralise the toxin by a mechanism which reducesthe loss of measurable TEER activity, to stimulate or assist the hostsnatural immune response, to catalyse or assist in immune clearance ofthe pathogen (or toxin) and/or to educate the immune system to respondappropriately to the pathogen (or toxin).

The residues in antibody variable domains are conventionally numberedaccording to a system devised by Kabat et al. This system is set forthin Kabat et al., 1987, in Sequences of Proteins of ImmunologicalInterest, US Department of Health and Human Services, NIH, USA(hereafter “Kabat et al. (supra)”). This numbering system is used in thepresent specification except where otherwise indicated.

The Kabat residue designations do not always correspond directly withthe linear numbering of the amino acid residues. The actual linear aminoacid sequence may contain fewer or additional amino acids than in thestrict Kabat numbering corresponding to a shortening of, or insertioninto, a structural component, whether framework or complementaritydetermining region (CDR), of the basic variable domain structure. Thecorrect Kabat numbering of residues may be determined for a givenantibody by alignment of residues of homology in the sequence of theantibody with a “standard” Kabat numbered sequence.

The CDRs of the heavy chain variable domain are located at residues31-35 (CDR-H1), residues 50-65 (CDR-H2) and residues 95-102 (CDR-H3)according to the Kabat numbering system. However, according to Chothia(Chothia, C. and Lesk, A. M. J. Mol. Biol., 196, 901-917 (1987)), theloop equivalent to CDR-H1 extends from residue 26 to residue 32. Thusunless indicated otherwise ‘CDR-H1’ as employed herein is intended torefer to residues 26 to 35, as described by a combination of the Kabatnumbering system and Chothia's topological loop definition.

The CDRs of the light chain variable domain are located at residues24-34 (CDR-L1), residues 50-56 (CDR-L2) and residues 89-97 (CDR-L3)according to the Kabat numbering system.

Antibodies for use in the present invention may be obtained using anysuitable method known in the art. The toxin A and/or toxin Bpolypeptide/protein including fusion proteins, for example toxin-Fcfusions proteins or cells (recombinantly or naturally) expressing thepolypeptide (such as activated T cells) can be used to produceantibodies which specifically recognise the target toxins. The toxinpolypeptide may be the full length polypeptide or a biologically activefragment or derivative thereof.

Polypeptides may be prepared by processes well known in the art fromgenetically engineered host cells comprising expression systems or theymay be recovered from natural biological sources. In the presentapplication, the term “polypeptides” includes peptides, polypeptides andproteins. These are used interchangeably unless otherwise specified. Thesequence for TcdA from ribotype 027 is given in SEQ ID NO: 171 (Uniprotaccession number C9YJ37) and the sequence for TcdB from ribotype 027 isgiven is SEQ ID NO: 172 (Uniprot accession number C9YJ35).

The antigen polypeptide may in some instances be part of a largerprotein such as a fusion protein for example fused to an affinity tag.

Antibodies generated against the antigen polypeptide may be obtained,where immunisation of an animal is necessary, by administering thepolypeptides to an animal, preferably a non-human animal, usingwell-known and routine protocols, see for example Handbook ofExperimental Immunology, D. M. Weir (ed.), Vol 4, Blackwell ScientificPublishers, Oxford, England, 1986). Many warm-blooded animals, such asrabbits, mice, rats, sheep, cows, camels or pigs may be immunized.However, mice, rabbits, pigs and rats are generally most suitable.

Monoclonal antibodies may be prepared by any method known in the artsuch as the hybridoma technique (Kohler & Milstein, 1975, Nature,256:495-497), the trioma technique, the human B-cell hybridoma technique(Kozbor et al., 1983, Immunology Today, 4:72) and the EBV-hybridomatechnique (Cole et al., Monoclonal Antibodies and Cancer Therapy, pp77-96, Alan R Liss, Inc., 1985).

Antibodies for use in the invention may also be generated using singlelymphocyte antibody methods by cloning and expressing immunoglobulinvariable region cDNAs generated from single lymphocytes selected for theproduction of specific antibodies by, for example, the methods describedby Babcook, J. et al., 1996, Proc. Natl. Acad. Sci. USA93(15):7843-78481; WO92/02551; WO2004/051268 and International PatentApplication number WO2004/106377.

Humanised antibodies (which include CDR-grafted antibodies) are antibodymolecules having one or more complementarity determining regions (CDRs)from a non-human species and a framework region from a humanimmunoglobulin molecule (see, e.g. U.S. Pat. No. 5,585,089; WO91/09967).It will be appreciated that it may only be necessary to transfer thespecificity determining residues of the CDRs rather than the entire CDR(see for example, Kashmiri et al., 2005, Methods, 36, 25-34). Humanisedantibodies may optionally further comprise one or more frameworkresidues derived from the non-human species from which the CDRs werederived.

As used herein, the term ‘humanised antibody molecule’ refers to anantibody molecule wherein the heavy and/or light chain contains one ormore CDRs (including, if desired, one or more modified CDRs) from adonor antibody (e.g. a murine monoclonal antibody) grafted into a heavyand/or light chain variable region framework of an acceptor antibody(e.g. a human antibody). For a review, see Vaughan et al, NatureBiotechnology, 16, 535-539, 1998. In one embodiment rather than theentire CDR being transferred, only one or more of the specificitydetermining residues from any one of the CDRs described herein above aretransferred to the human antibody framework (see for example, Kashmiriet al., 2005, Methods, 36, 25-34). In one embodiment only thespecificity determining residues from one or more of the CDRs describedherein above are transferred to the human antibody framework. In anotherembodiment only the specificity determining residues from each of theCDRs described herein above are transferred to the human antibodyframework.

When the CDRs or specificity determining residues are grafted, anyappropriate acceptor variable region framework sequence may be usedhaving regard to the class/type of the donor antibody from which theCDRs are derived, including mouse, primate and human framework regions.Suitably, the humanised antibody according to the present invention hasa variable domain comprising human acceptor framework regions as well asone or more of the CDRs provided herein.

Thus, provided in one embodiment is a humanised antibody which bindstoxin A or toxin B wherein the variable domain comprises human acceptorframework regions and non-human donor CDRs.

Examples of human frameworks which can be used in the present inventionare KOL, NEWM, REI, EU, TUR, TEI, LAY and POM (Kabat et al., supra). Forexample, KOL and NEWM can be used for the heavy chain, REI can be usedfor the light chain and EU, LAY and POM can be used for both the heavychain and the light chain. Alternatively, human germline sequences maybe used; these are available at: http://vbase.mrc-cpe.cam.ac.uk/

In a humanised antibody of the present invention, the acceptor heavy andlight chains do not necessarily need to be derived from the sameantibody and may, if desired, comprise composite chains having frameworkregions derived from different chains.

Also, in a humanised antibody of the present invention, the frameworkregions need not have exactly the same sequence as those of the acceptorantibody. For instance, unusual residues may be changed to morefrequently-occurring residues for that acceptor chain class or type.Alternatively, selected residues in the acceptor framework regions maybe changed so that they correspond to the residue found at the sameposition in the donor antibody (see Reichmann et al., 1998, Nature, 332,323-324). Such changes should be kept to the minimum necessary torecover the affinity of the donor antibody. A protocol for selectingresidues in the acceptor framework regions which may need to be changedis set forth in WO 91/09967.

Generally the antibody sequences disclosed in the present specificationare humanised.

The invention also provides sequences which are 80%, 90%, 91%, 92%, 93%94%, 95% 96%, 97%, 98% or 99% similar to a sequence or antibodydisclosed herein.

“Identity”, as used herein, indicates that at any particular position inthe aligned sequences, the amino acid residue is identical between thesequences. “Similarity”, as used herein, indicates that, at anyparticular position in the aligned sequences, the amino acid residue isof a similar type between the sequences. For example, leucine may besubstituted for isoleucine or valine. Other amino acids which can oftenbe substituted for one another include but are not limited to:

-   -   phenylalanine, tyrosine and tryptophan (amino acids having        aromatic side chains);    -   lysine, arginine and histidine (amino acids having basic side        chains);    -   aspartate and glutamate (amino acids having acidic side chains);    -   asparagine and glutamine (amino acids having amide side chains);        and    -   cysteine and methionine (amino acids having sulphur-containing        side chains).

Degrees of identity and similarity can be readily calculated(Computational Molecular Biology, Lesk, A. M., ed., Oxford UniversityPress, New York, 1988; Biocomputing. Informatics and Genome Projects,Smith, D. W., ed., Academic Press, New York, 1993; Computer Analysis ofSequence Data, Part 1, Griffin, A. M., and Griffin, H. G., eds., HumanaPress, New Jersey, 1994; Sequence Analysis in Molecular Biology, vonHeinje, G., Academic Press, 1987, Sequence Analysis Primer, Gribskov, M.and Devereux, J., eds., M Stockton Press, New York, 1991, the BLAST™software available from NCBI (Altschul, S. F. et al., 1990, J. Mol.Biol. 215:403-410; Gish, W. & States, D. J. 1993, Nature Genet.3:266-272. Madden, T. L. et al., 1996, Meth. Enzymol. 266:131-141;Altschul, S. F. et al., 1997, Nucleic Acids Res. 25:3389-3402; Zhang, J.& Madden, T. L. 1997, Genome Res. 7:649-656,).

The antibody molecules of the present invention include a completeantibody molecule having full length heavy and light chains or afragment thereof and may be, but are not limited to Fab, modified Fab,Fab′, modified Fab′, F(ab′)2, Fv, Fab-Fv, Fab-dsFv, single domainantibodies (e.g. VH or VL or VHH), scFv, bi, tri or tetra-valentantibodies, Bis-scFv, diabodies, triabodies, tetrabodies andepitope-binding fragments of any of the above (see for example Holligerand Hudson, 2005, Nature Biotech. 23(9):1126-1136; Adair and Lawson,2005, Drug Design Reviews—Online 2(3), 209-217). The methods forcreating and manufacturing these antibody fragments are well known inthe art (see for example Verma et al., 1998, Journal of ImmunologicalMethods, 216, 165-181). Other antibody fragments for use in the presentinvention include the Fab and Fab′ fragments described in Internationalpatent applications WO2005/003169, WO2005/003170 and WO2005/003171.Multi-valent antibodies may comprise multiple specificities e.gbispecific or may be monospecific (see for example WO 92/22853 andWO05/113605). Bispecific and multispecific antibody variants areespecially considered in this example since the aim is to neutralise twoindependent target proteins: TcdA and TcdB. Variable regions fromantibodies disclosed herein may be configured in such a way as toproduce a single antibody variant which is capable of binding to andneutralising TcdA and TcdB.

In one embodiment the antibody according to the present disclosure isprovided as TcdA or TcdB binding antibody fusion protein which comprisesan immunoglobulin moiety, for example a Fab or Fab′ fragment, and one ortwo single domain antibodies (dAb) linked directly or indirectlythereto, for example as described in WO2009/040562.

In one embodiment the fusion protein comprises two domain antibodies,for example as a variable heavy (VH) and variable light (VL) pairing,optionally linked by a disulphide bond, for example as described inWO2010/035012.

In one embodiment the Fab or Fab′ element of the fusion protein has thesame or similar specificity to the single domain antibody or antibodies.In one embodiment the Fab or Fab′ has a different specificity to thesingle domain antibody or antibodies, that is to say the fusion proteinis multivalent. In one embodiment a multivalent fusion protein accordingto the present invention has an albumin binding site, for example aVH/VL pair therein provides an albumin binding site.

In one embodiment the multivalent fusion protein according to theinvention binds TcdA and TcdB.

In one embodiment the multivalent fusion protein according to theinvention binds TcdB in multiple positions, for example has distinctbinding regions specific for two different epitopes.

The constant region domains of the antibody molecule of the presentinvention, if present, may be selected having regard to the proposedfunction of the antibody molecule, and in particular the effectorfunctions which may be required. For example, the constant regiondomains may be human IgA, IgD, IgE, IgG or IgM domains. In particular,human IgG constant region domains may be used, especially of the IgG1and IgG3 isotypes when the antibody molecule is intended for therapeuticuses and antibody effector functions are required. Alternatively, IgG2and IgG4 isotypes may be used when the antibody molecule is intended fortherapeutic purposes and antibody effector functions are not required,e.g. for simply neutralising or agonising an antigen. It will beappreciated that sequence variants of these constant region domains mayalso be used. For example IgG4 molecules in which the serine at position241 has been changed to proline as described in Angal et al., MolecularImmunology, 1993, 30 (1), 105-108 may be used. It will also beunderstood by one skilled in the art that antibodies may undergo avariety of posttranslational modifications. The type and extent of thesemodifications often depends on the host cell line used to express theantibody as well as the culture conditions. Such modifications mayinclude variations in glycosylation, methionine oxidation,diketopiperazine formation, aspartate isomerization and asparaginedeamidation. A frequent modification is the loss of a carboxy-terminalbasic residue (such as lysine or arginine) due to the action ofcarboxypeptidases (as described in Harris, R J. Journal ofChromatography 705:129-134, 1995).

In one embodiment the antibody heavy chain comprises a CH1 domain andthe antibody light chain comprises a CL domain, either kappa or lambda.

Biological molecules, such as antibodies or fragments, contain acidicand/or basic functional groups, thereby giving the molecule a netpositive or negative charge. The amount of overall “observed” chargewill depend on the absolute amino acid sequence of the entity, the localenvironment of the charged groups in the 3D structure and theenvironmental conditions of the molecule. The isoelectric point (pI) isthe pH at which a particular molecule or solvent accessible surfacethereof carries no net electrical charge. In one example, the antibodyand fragments of the invention may be engineered to have an appropriateisoelectric point. This may lead to antibodies and/or fragments withmore robust properties, in particular suitable solubility and/orstability profiles and/or improved purification characteristics.

Thus in one aspect the invention provides a humanised antibodyengineered to have an isoelectric point different to that of theoriginally identified antibody from which it is derived. The antibodymay, for example be engineered by replacing an amino acid residue suchas replacing an acidic amino acid residue with one or more basic aminoacid residues. Alternatively, basic amino acid residues may beintroduced or acidic amino acid residues can be removed. Alternatively,if the molecule has an unacceptably high pI value acidic residues may beintroduced to lower the pI, as required. It is important that whenmanipulating the pI care must be taken to retain the desirable activityof the antibody or fragment. Thus in one embodiment the engineeredantibody or fragment has the same or substantially the same activity asthe “unmodified” antibody or fragment.

Programs such as ** ExPASY http://www.expasy.ch/tools/pi_tool.html, andhttp://www.iut-arles.up.univ-mrs.fr/w3bb/d_abim/compo-p.html, may beused to predict the isoelectric point of the antibody or fragment.

It will be appreciated that the affinity of antibodies provided by thepresent invention may be altered using any suitable method known in theart. The affinity of the antibodies or variants thereof may be measuredusing any suitable method known in the art, including BIAcore, using anappropriate isolated natural or recombinant protein or a suitable fusionprotein/polypeptide.

The present invention therefore also relates to variants of the antibodymolecules of the present invention, which have an improved affinity forTcdA or TcdB, as appropriate. Such variants can be obtained by a numberof affinity maturation protocols including mutating the CDRs (Yang etal., J. Mol. Biol., 254, 392-403, 1995), chain shuffling (Marks et al.,Bio/Technology, 10, 779-783, 1992), use of mutator strains of E. coli(Low et al., J. Mol. Biol., 250, 359-368, 1996), DNA shuffling (Pattenet al., Curr. Opin. Biotechnol., 8, 724-733, 1997), phage display(Thompson et al., J. Mol. Biol., 256, 77-88, 1996) and sexual PCR(Crameri et al., Nature, 391, 288-291, 1998). Vaughan et al. (supra)discusses these methods of affinity maturation.

Improved affinity as employed herein in this context refers to animprovement refers to an improvement over the starting molecule.

If desired an antibody for use in the present invention may beconjugated to one or more effector molecule(s). It will be appreciatedthat the effector molecule may comprise a single effector molecule ortwo or more such molecules so linked as to form a single moiety that canbe attached to the antibodies of the present invention. Where it isdesired to obtain an antibody fragment linked to an effector molecule,this may be prepared by standard chemical or recombinant DNA proceduresin which the antibody fragment is linked either directly or via acoupling agent to the effector molecule. Techniques for conjugating sucheffector molecules to antibodies are well known in the art (see,Hellstrom et al., Controlled Drug Delivery, 2nd Ed., Robinson et al.,eds., 1987, pp. 623-53; Thorpe et al., 1982, Immunol. Rev., 62:119-58and Dubowchik et al., 1999, Pharmacology and Therapeutics, 83, 67-123).Particular chemical procedures include, for example, those described inWO 93/06231, WO 92/22583, WO 89/00195, WO 89/01476 and WO03031581.Alternatively, where the effector molecule is a protein or polypeptidethe linkage may be achieved using recombinant DNA procedures, forexample as described in WO 86/01533 and EP0392745.

The term effector molecule as used herein includes, for example,biologically active proteins, for example enzymes, other antibody orantibody fragments, synthetic or naturally occurring polymers, nucleicacids and fragments thereof e.g. DNA, RNA and fragments thereof,radionuclides, particularly radioiodide, radioisotopes, chelated metals,nanoparticles and reporter groups such as fluorescent compounds orcompounds which may be detected by NMR or ESR spectroscopy.

Other effector molecules may include chelated radionuclides such as111In and 90Y, Lu177, Bismuth213, Californium252, Iridium192 andTungsten188/Rhenium188; or drugs such as but not limited to,alkylphosphocholines, topoisomerase I inhibitors, taxoids and suramin.

Other effector molecules include proteins, peptides and enzymes. Enzymesof interest include, but are not limited to, proteolytic enzymes,hydrolases, lyases, isomerases, transferases. Proteins, polypeptides andpeptides of interest include, but are not limited to, immunoglobulins,toxins such as abrin, ricin A, Pseudomonas exotoxin, or diphtheriatoxin, a protein such as insulin, tumour necrosis factor, α-interferon,β-interferon, nerve growth factor, platelet derived growth factor ortissue plasminogen activator, a thrombotic agent or an anti-angiogenicagent, e.g. angiostatin or endostatin, or, a biological responsemodifier such as a lymphokine, interleukin-1 (IL-1), interleukin-2(IL-2), granulocyte macrophage colony stimulating factor (GM-CSF),granulocyte colony stimulating factor (G-CSF), nerve growth factor (NGF)or other growth factor and immunoglobulins.

Other effector molecules may include detectable substances useful forexample in diagnosis. Examples of detectable substances include variousenzymes, prosthetic groups, fluorescent materials, luminescentmaterials, bioluminescent materials, radioactive nuclides, positronemitting metals (for use in positron emission tomography), andnonradioactive paramagnetic metal ions. See generally U.S. Pat. No.4,741,900 for metal ions which can be conjugated to antibodies for useas diagnostics. Suitable enzymes include horseradish peroxidase,alkaline phosphatase, beta-galactosidase, or acetylcholinesterase;suitable prosthetic groups include streptavidin, avidin and biotin;suitable fluorescent materials include umbelliferone, fluorescein,fluorescein isothiocyanate, rhodamine, dichlorotriazinylaminefluorescein, dansyl chloride and phycoerythrin; suitable luminescentmaterials include luminol; suitable bioluminescent materials includeluciferase, luciferin, and aequorin; and suitable radioactive nuclidesinclude 125I, 131I, 111In and 99Tc.

In another example the effector molecule may increase the half-life ofthe antibody in vivo, and/or reduce immunogenicity of the antibodyand/or enhance the delivery of an antibody across an epithelial barrierto the immune system. Examples of suitable effector molecules of thistype include polymers, albumin, albumin binding proteins or albuminbinding compounds such as those described in WO05/117984.

Where the effector molecule is a polymer it may, in general, be asynthetic or a naturally occurring polymer, for example an optionallysubstituted straight or branched chain polyalkylene, polyalkenylene orpolyoxyalkylene polymer or a branched or unbranched polysaccharide, e.g.a homo- or hetero-polysaccharide.

Specific optional substituents which may be present on theabove-mentioned synthetic polymers include one or more hydroxy, methylor methoxy groups.

Specific examples of synthetic polymers include optionally substitutedstraight or branched chain poly(ethyleneglycol), poly(propyleneglycol)poly(vinylalcohol) or derivatives thereof, especially optionallysubstituted poly(ethyleneglycol) such as methoxypoly(ethyleneglycol) orderivatives thereof.

Specific naturally occurring polymers include lactose, amylose, dextran,glycogen or derivatives thereof.

“Derivatives” as used herein is intended to include reactivederivatives, for example thiol-selective reactive groups such asmaleimides and the like. The reactive group may be linked directly orthrough a linker segment to the polymer. It will be appreciated that theresidue of such a group will in some instances form part of the productas the linking group between the antibody fragment and the polymer.

The size of the polymer may be varied as desired, but will generally bein an average molecular weight range from 500 Da to 50000 Da, forexample from 5000 to 40000 Da such as from 20000 to 40000 Da. Thepolymer size may in particular be selected on the basis of the intendeduse of the product for example ability to localize to certain tissuessuch as tumors or extend circulating half-life (for review see Chapman,2002, Advanced Drug Delivery Reviews, 54, 531-545). Thus, for example,where the product is intended to leave the circulation and penetratetissue, for example for use in the treatment of a tumour, it may beadvantageous to use a small molecular weight polymer, for example with amolecular weight of around 5000 Da. For applications where the productremains in the circulation, it may be advantageous to use a highermolecular weight polymer, for example having a molecular weight in therange from 20000 Da to 40000 Da.

Suitable polymers include a polyalkylene polymer, such as apoly(ethyleneglycol) or, especially, a methoxypoly(ethyleneglycol) or aderivative thereof, and especially with a molecular weight in the rangefrom about 15000 Da to about 40000 Da.

In one example antibodies for use in the present invention are attachedto poly(ethyleneglycol) (PEG) moieties. In one particular example theantibody is an antibody fragment and the PEG molecules may be attachedthrough any available amino acid side-chain or terminal amino acidfunctional group located in the antibody fragment, for example any freeamino, imino, thiol, hydroxyl or carboxyl group. Such amino acids mayoccur naturally in the antibody fragment or may be engineered into thefragment using recombinant DNA methods (see for example U.S. Pat. Nos.5,219,996; 5,667,425; WO98/25971, WO2008/038024). In one example theantibody molecule of the present invention is a modified Fab fragmentwherein the modification is the addition to the C-terminal end of itsheavy chain one or more amino acids to allow the attachment of aneffector molecule. Suitably, the additional amino acids form a modifiedhinge region containing one or more cysteine residues to which theeffector molecule may be attached. Multiple sites can be used to attachtwo or more PEG molecules.

Suitably PEG molecules are covalently linked through a thiol group of atleast one cysteine residue located in the antibody fragment. Eachpolymer molecule attached to the modified antibody fragment may becovalently linked to the sulphur atom of a cysteine residue located inthe fragment. The covalent linkage will generally be a disulphide bondor, in particular, a sulphur-carbon bond. Where a thiol group is used asthe point of attachment appropriately activated effector molecules, forexample thiol selective derivatives such as maleimides and cysteinederivatives may be used. An activated polymer may be used as thestarting material in the preparation of polymer-modified antibodyfragments as described above. The activated polymer may be any polymercontaining a thiol reactive group such as an α-halocarboxylic acid orester, e.g. iodoacetamide, an imide, e.g. maleimide, a vinyl sulphone ora disulphide. Such starting materials may be obtained commercially (forexample from Nektar, formerly Shearwater Polymers Inc., Huntsville,Ala., USA) or may be prepared from commercially available startingmaterials using conventional chemical procedures. Particular PEGmolecules include 20K methoxy-PEG-amine (obtainable from Nektar,formerly Shearwater; Rapp Polymere; and SunBio) and M-PEG-SPA(obtainable from Nektar, formerly Shearwater).

In one embodiment, the antibody is a modified Fab fragment or diFabwhich is PEGylated, i.e. has PEG (poly(ethyleneglycol)) covalentlyattached thereto, e.g. according to the method disclosed in EP 0948544or EP1090037 [see also “Poly(ethyleneglycol) Chemistry, Biotechnical andBiomedical Applications”, 1992, J. Milton Harris (ed), Plenum Press, NewYork, “Poly(ethyleneglycol) Chemistry and Biological Applications”,1997, J. Milton Harris and S. Zalipsky (eds), American Chemical Society,Washington D.C. and “Bioconjugation Protein Coupling Techniques for theBiomedical Sciences”, 1998, M. Aslam and A. Dent, Grove Publishers, NewYork; Chapman, A. 2002, Advanced Drug Delivery Reviews 2002,54:531-545]. In one example PEG is attached to a cysteine in the hingeregion. In one example, a PEG modified Fab fragment has a maleimidegroup covalently linked to a single thiol group in a modified hingeregion. A lysine residue may be covalently linked to the maleimide groupand to each of the amine groups on the lysine residue may be attached amethoxypoly(ethyleneglycol) polymer having a molecular weight ofapproximately 20,000 Da. The total molecular weight of the PEG attachedto the Fab fragment may therefore be approximately 40,000 Da.

Particular PEG molecules include 2-[3-(N-maleimido)propionamido]ethylamide of N,N′-bis(methoxypoly(ethylene glycol) MW 20,000) modifiedlysine, also known as PEG2MAL40K (obtainable from Nektar, formerlyShearwater).

Alternative sources of PEG linkers include NOF who supply GL2-400MA2(wherein m in the structure below is 5) and GL2-400MA (where m is 2) andn is approximately 450:

That is to say each PEG is about 20,000 Da.

Further alternative PEG effector molecules of the following type:

are available from Dr Reddy, NOF and Jenkem.

In one embodiment there is provided an antibody which is PEGylated (forexample with a PEG described herein), attached through a cysteine aminoacid residue at or about amino acid 226 in the chain, for example aminoacid 226 of the heavy chain (by sequential numbering).

In one embodiment one certain antibodies according to the presentdisclosure have the following properties:

Affinity (pM) Valency of binding Antibody TcdA₁₂₃ TcdA₄₅₆ TcdA, est.EC₅₀ (ng/ml) CA922 4.06 2.59 16  1.21 CA923 64.7 312 12 160.42  CA995nil 119  1 37.64 CA997 132 66.8 12  6.25 CA1000 73.3 84.1  2 19.73

The present invention also provides compositions such as apharmaceutical composition of antibody or combination of antibodiesdefined herein.

The present invention also provides a composition that comprises atleast two antibodies according to the invention, for example wherein atleast one antibody therein is specific to TcdA and at least one antibodytherein is specific to TcdB or alternatively at least two antibodiesspecific to TcdA or at least two antibodies specific to TcdB.

In one embodiment there is provided a composition that comprisesmultiple antibodies specific to TcdA and optionally one or moreantibodies specific to TcdB.

In one embodiment there is provided a composition that comprisesmultiple antibodies specific to TcdB and optionally one or moreantibodies specific to TcdA.

Thus in one embodiment there is provided a composition comprising 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15 antibodies according to theinvention i.e. distinct antibodies.

The invention describes one particular mixture comprising 3 Mabs, oneMab of which is specific for TcdA and two Mabs of which are specific forTcdB. This mixture demonstrated very high levels of protection fromdeath and gut inflammation from a lethal infective oral dose ofClostridium difficile in hamsters.

In particular there is provided a composition comprising a combinationof one anti-TcdA antibody comprising a heavy variable region with asequence as shown in SEQ ID NO:49 and a light variable region with asequence shown in SEQ ID NO: 47 and two anti-TcdB the first with a heavyvariable region shown in SEQ ID NO: 129 and a light variable regionshown in SEQ ID NO: 127, and the second with a heavy variable regionshown in SEQ ID NO: 159 and light variable region shown in SEQ ID NO:157.

In one embodiment wherein the composition comprises 3 antibodies, suchas one anti-TcdA and two anti-TcdB antibodies the antibodies are in theratio of 50%, 25% and 25% respectively of the total antibody contentthereof.

In one embodiment there is provided a composition comprising 2, 3, 4 or5 antibodies specific to TcdA and optionally 1, 2, 3, 4 or 5 antibodiesspecific to TcdB.

In one embodiment the compositions provided according to the inventionare well defined, for example are mixtures of monoclonal antibodiesrather than simply polyclonal compositions derived from an immunised orimmune competent host.

In one embodiment the composition of antibodies has an EC₅₀ of 200 ng/mlor less, for example 150 ng/ml or less, such as 100 ng/ml or less, suchas 0.1 to 10 ng/ml.

Advantageously the antibodies described herein have very high levels ofbiophysical stability and so are suitable for inclusion in mixtures ofantibodies.

In one aspect a pharmaceutical formulation or composition according tothe invention further comprises a pharmaceutically acceptable excipient.

Pharmaceutically acceptable carriers in therapeutic compositions mayadditionally contain liquids such as water, saline, glycerol andethanol. Additionally, auxiliary substances, such as wetting oremulsifying agents or pH buffering substances, may be present in suchcompositions. Such carriers enable the pharmaceutical compositions to beformulated as tablets, pills, dragees, capsules, liquids, gels, syrups,slurries and suspensions, for ingestion by the patient.

Suitable forms for administration include forms suitable for parenteraladministration, e.g. by injection or infusion, for example by bolusinjection or continuous infusion. Where the product is for injection orinfusion, it may take the form of a suspension, solution or emulsion inan oily or aqueous vehicle and it may contain formulatory agents, suchas suspending, preservative, stabilising and/or dispersing agents.Alternatively, the antibody molecule may be in dry form, forreconstitution before use with an appropriate sterile liquid.

Once formulated, the compositions of the invention can be administereddirectly to the subject. The subjects to be treated can be animals.However, in one or more embodiments the compositions are adapted foradministration to human subjects.

Suitably in formulations according to the present disclosure, the pH ofthe final formulation is not similar to the value of the isoelectricpoint of the antibody or fragment, for example if the pH of theformulation is 7 then a pI of from 8-9 or above may be appropriate.Whilst not wishing to be bound by theory it is thought that this mayultimately provide a final formulation with improved stability, forexample the antibody or fragment remains in solution.

In one embodiment the composition or formulation of the presentdisclosure comprises 1-200 mg/mL of antibodies, that this to say thecombined antibody content, for example 150 mg/mL or less, such as 100mg/mL or less, in particular 90, 80, 70, 60, 50, 40, 30, 20, 10 mg/mL orless.

In one embodiment a composition or formulation according to the presentdisclosure comprises 20 mg/mL of each antibody therein.

In one embodiment there is provided a formulation comprising:

-   -   33 mg/mL or less of one anti-TcdA antibody comprising a heavy        variable region with a sequence as shown in SEQ ID NO: 49 and a        light variable region with a sequence shown in SEQ ID NO: 47,        and    -   28 mg/mL or less of a first anti-TcdB with a heavy variable        region shown in SEQ ID NO: 129 and a light variable region shown        in SEQ ID NO: 127, and 25 mg/mL of a second anti-TcdB with a        heavy variable region shown in SEQ ID NO: 159 and light variable        region shown in SEQ ID NO: 157.

In one embodiment the pharmaceutical formulation at a pH in the range of4.0 to 7.0 comprises: 1 to 200 mg/mL of an antibody according to thepresent disclosure, 1 to 100 mM of a buffer, 0.001 to 1% of asurfactant,

a) 10 to 500 mM of a stabiliser,

b) 5 to 500 mM of a tonicity agent, or

c) 10 to 500 mM of a stabiliser and 5 to 500 mM of a tonicity agent.

In one embodiment the composition or formulation according to thepresent disclosure comprises the buffer phosphate buffered saline.

For example the formulation at approximately pH6 may comprise 1 to 50mg/mL of antibody, 20 mM L-histidine HCl, 240 mM trehalose and 0.02%polysorbate 20. Alternatively a formulation at approximately pH 5.5 maycomprise 1 to 50 mg/mL of antibody, 20 mM citrate buffer, 240 mMsucrose, 20 mM arginine, and 0.02% polysorbate 20.

The pharmaceutical compositions of this invention may be administered byany number of routes including, but not limited to, oral, intravenous,intramuscular, intra-arterial, intramedullary, intrathecal,intraventricular, transdermal, transcutaneous (for example, seeWO98/20734), subcutaneous, intraperitoneal, intranasal, enteral,topical, sublingual, intravaginal or rectal routes. Hyposprays may alsobe used to administer the pharmaceutical compositions of the invention.Typically, the therapeutic compositions may be prepared as injectables,either as liquid solutions or suspensions. Solid forms suitable forsolution in, or suspension in, liquid vehicles prior to injection mayalso be prepared.

Direct delivery of the compositions will generally be accomplished byinjection, subcutaneously, intraperitoneally, intravenously orintramuscularly, or delivered to the interstitial space of a tissue.

The compositions can also be administered into a lesion or directly intothe gastrointestinal tract by for examples, encapsulated oral dosage forswallowing, through a nasogastric tube to the stomach or ileum, througha rectal tube or enema solutions or by rectal capsule. Dosage treatmentmay be a single dose schedule or a multiple dose schedule.

It will be appreciated that the active ingredient in the compositionwill be an antibody molecule. As such, it will be susceptible todegradation in the gastrointestinal tract. Thus, if the composition isto be administered by a route using the gastrointestinal tract, thecomposition will need to contain agents which protect the antibody fromdegradation but which release the antibody once it has been absorbedfrom the gastrointestinal tract.

A thorough discussion of pharmaceutically acceptable carriers isavailable in Remington's Pharmaceutical Sciences (Mack PublishingCompany, N.J. 1991).

The present invention also provides an antibody or antibody combinationor a composition comprising the same, as described herein, fortreatment, for example for the treatment or prophylaxis of C. difficileinfection or complications associated with the same such as diarrhoea,colitis in particular pseudomembranous colitis, bloating, abdominal painand toxic megacolon.

Prophylaxis can also be achieved by the administration of pre-formedcomplexes of inactivated toxin antigen (toxoid) and antibody in order tocreate a vaccine.

In one embodiment the antibodies, combinations thereof and compositionscomprising the same according to the invention are suitable for treatinginfection with so-called super strains of C. difficile, i.e.hypervirulent strains such as ribotype 027.

The antibodies and compositions according to the present invention aresuitable for use in the treatment or prophylaxis of acute and/or chroniceffects of the relevant C. difficile toxins during primary infection.

The antibodies and compositions according to the present invention aresuitable for use in the treatment or prophylaxis of effects of therelevant C. difficile toxins during secondary infection or re-infection.International guidelines enshrine time intervals after a primaryinfection which hence defines a secondary (or recurrent) infection asbeing distinct from a continuation of existing symptoms sometimesdescribed as a relapse (29). Research has shown that secondaryinfections can be the result of the same strain or ribotype as theprimary infection. In such cases recurrence rather than relapse relieson agreed temporal constraints. However, research also clearly showsthat secondary infection can also be the result of infection of a strainor ribotype distinct from that of the primary infection. In one study,48% of disease recurrences were the result of a second strain distinctfrom that having caused the first infection (30). In another study, morethan 56% of disease recurrences were the result of a second straindistinct from that having caused the first infection (31).

In one embodiment the antibodies, combinations thereof and compositionscomprising the same according to the invention are suitable for use inthe prevention of damage, for example long term structural damage to theepithelium of the colon.

In one embodiment the antibodies, combinations and composition aresuitable for preventing C. difficile infection including recurrence ofinfection, in particular nosocomial infection.

In one embodiment the antibodies, combinations thereof and compositionscomprising the same according to the invention are suitable for reducingthe risk of recurrence of C. difficile infection.

Advantageously, the antibodies of the present disclosure can beadministered prophylactically to prevent infection or re-infectionbecause in the absence of toxin to which the antibody is specific theantibody is simply to be cleared from the body without causing adverseinteractions with the subjects body tissues.

Advantageously the antibodies of the present disclosure seem to elicit arapid response after administration, for example within one or two daysof administration rapid clearance of the target toxin is invoked, thismay prevent vital organs such as the lungs, heart and kidneys beingdamaged. This is the first time that agents have been made availablewith can be employed to prevent damage or injury to a patient by toxinsA and/or B in the acute C. difficile infection stage.

Thus in one embodiment the antibodies, combinations thereof andcompositions comprising the same according to the invention are suitablefor preventing damage to vital organs.

In one embodiment the antibody, combinations or formulations describedherein are suitable for preventing death of an infected patient, ifadministered within an appropriate time frame before irreparable damagehas been done by the toxins.

The antibodies of the present disclosure have fast on-rates, whichfacilitates the rapid effect in vivo.

In one embodiment the patient population is over 60, such as over 65years of age.

In one embodiment the patient population is 5 years old or less.

The antibodies according the invention may be employed in combinationwith antibiotic treatment for example metronidazole, vancomycin orfidaxomicin.

A range of in vitro data exemplify the properties of the Mabs and Mabmixtures. We show that one mixture of 3 Mabs (50% molar quantities ofanti-TcdA and 50% molar quantities of anti-TcdB components) was able toprotect hamsters from a lethal CDI.

In one embodiment there is provided a method of treating a patient inneed thereof by administering a therapeutically effective amount of anantibody as described herein or antibody combination or a compositioncomprising the same, for example in the treatment or prophylaxis of C.difficile infection or complications associated with the same such asdiarrhoea, colitis in particular pseudomembranous colitis, bloating,abdominal pain and toxic megacolon.

In one embodiment the antibody, combination or formulation isadministered by a parenteral route, for example subcutaneously,intraperitoneally, intravenously or intramuscularly. The data in theExamples generated in hamsters indicates that the doses administered bythis route reach the gut and thus are able to generate a therapeuticeffect.

In one embodiment the antibody, combination or formulation isadministered orally, for example an enterically coated formulation.

In one embodiment there is provided use of an antibody, combination orformulation as described herein for the manufacture of a medicament forthe treatment or prophylaxis of C. difficile infection.

In one embodiment the dose administered is in the range 1 to 1000 mg/Kg,for example 10 to 75 mg/Kg, such 20 to 50 mg/Kg.

In one embodiment the half-life of the antibody or antibodies in miceand hamsters in vivo is in the range 6 to 8 days in healthy (uninfected)animals and hence are expected to have half-lives in humans in the rangeof 14-28 days.

In one embodiment the antibody or antibodies are given as one dose only.

In one embodiment the antibody or antibodies are given as a weekly orbiweekly dose.

In one embodiment the antibody or antibodies are given as once dailydoses.

In one embodiment there is provided complex comprising TcdA or animmunogenic fragment thereof, complexed with one or more anti-TcdAantibodies defined herein. The complex may be employed as the antigen ina vaccine formulation, for example suitable for generating protectiveantibodies to toxin A in vivo after administration to a human.

In one embodiment there is provided complex comprising TcdB or animmunogenic fragment thereof, complexed with one or more anti-TcdBantibodies defined herein. The complex may be employed as the antigen ina vaccine formulation, for example suitable for generating protectiveantibodies to toxin B in vivo after administration to a human.

Th1-type immunostimulants which may be formulated to produce adjuvantssuitable for use in the present invention include and are not restrictedto the following.

In one embodiment there is provided a complex comprising TcdA or animmunogenic fragment thereof and TcdB or an immunogenic fragmentthereof, wherein each toxin or fragment is complexed with one or moreantibodies specific thereto, wherein the complex is suitable foradministration as a vaccine formulation.

Antibody:antigen complexes are known to be taken up by the immune systemin an Fc receptor mediated process (27, 28) and pre-formed complexes ofantibody:antigen complexes have been successfully use as vaccines inhuman clinical trials (22).

In one or more embodiments the vaccine formulation further comprises anadjuvant as an immunostimulant.

Monophosphoryl lipid A, in particular 3-de-O-acylated monophosphoryllipid A (3D-MPL), is a preferred Th1-type immunostimulant for use in theinvention. 3D-MPL is a well known adjuvant manufactured by RibiImmunochem, Montana. Chemically it is often supplied as a mixture of3-de-O-acylated monophosphoryl lipid A with either 4, 5, or 6 acylatedchains. It can be purified and prepared by the methods taught in GB2122204B, which reference also discloses the preparation of diphosphoryllipid A, and 3-O-deacylated variants thereof. Other purified andsynthetic lipopolysaccharides have been described (U.S. Pat. No.6,005,099 and EP 0 729 473 B1; Hilgers et al., 1986, Int. Arch. Allergy.Immunol., 79(4):392-6; Hilgers et al., 1987, Immunology, 60(1):141-6;and EP 0 549 074 B1). A preferred form of 3D-MPL is in the form of aparticulate formulation having a small particle size less than 0.2 mm indiameter, and its method of manufacture is disclosed in EP 0 689 454.

Saponins are also preferred Th1 immunostimulants in accordance with theinvention. Saponins are well known adjuvants and are taught in:Lacaille-Dubois, M and Wagner H. (1996. A review of the biological andpharmacological activities of saponins. Phytomedicine vol 2 pp 363-386).For example, Quil A (derived from the bark of the South American treeQuillaja Saponaria Molina), and fractions thereof, are described in U.S.Pat. No. 5,057,540 and “Saponins as vaccine adjuvants”, Kensil, C. R.,Crit Rev Ther Drug Carrier Syst, 1996, 12 (1-2):1-55; and EP 0 362 279B1. The haemolytic saponins QS21 and QS17 (HPLC purified fractions ofQuil A) have been described as potent systemic adjuvants, and the methodof their production is disclosed in U.S. Pat. No. 5,057,540 and EP 0 362279 B1. Also described in these references is the use of QS7 (anon-haemolytic fraction of Quil-A) which acts as a potent adjuvant forsystemic vaccines. Use of QS21 is further described in Kensil et al.(1991. J. Immunology vol 146, 431-437). Combinations of QS21 andpolysorbate or cyclodextrin are also known (WO 99/10008). Particulateadjuvant systems comprising fractions of QuilA, such as QS21 and QS7 aredescribed in WO 96/33739 and WO 96/11711. One such system is known as anIscorn and may contain one or more saponins.

Another preferred immunostimulant is an immunostimulatoryoligonucleotide containing unmethylated CpG dinucleotides (“CpG”). CpGis an abbreviation for cytosine-guanosine dinucleotide motifs present inDNA. CpG is known in the art as being an adjuvant when administered byboth systemic and mucosal routes (WO 96/02555, EP 468520, Davis et al.,J. Immunol, 1998, 160(2):870-876; McCluskie and Davis, J. Immunol.,1998, 161(9):4463-6). Historically, it was observed that the DNAfraction of BCG could exert an anti-tumour effect. In further studies,synthetic oligonucleotides derived from BCG gene sequences were shown tobe capable of inducing immunostimulatory effects (both in vitro and invivo). The authors of these studies concluded that certain palindromicsequences, including a central CG motif, carried this activity. Thecentral role of the CG motif in immunostimulation was later elucidatedin a publication by Krieg, Nature 374, p 546 1995. Detailed analysis hasshown that the CG motif has to be in a certain sequence context, andthat such sequences are common in bacterial DNA but are rare invertebrate DNA. The immunostimulatory sequence is often: Purine, Purine,C, G, pyrimidine, pyrimidine; wherein the CG motif is not methylated,but other unmethylated CpG sequences are known to be immunostimulatoryand may be used in the present invention.

In certain combinations of the six nucleotides a palindromic sequence ispresent. Several of these motifs, either as repeats of one motif or acombination of different motifs, can be present in the sameoligonucleotide. The presence of one or more of these immunostimulatorysequences containing oligonucleotides can activate various immunesubsets, including natural killer cells (which produce interferon g andhave cytolytic activity) and macrophages (Wooldrige et al Vol 89 (no.8), 1977). Other unmethylated CpG containing sequences not having thisconsensus sequence have also now been shown to be immunomodulatory.

CpG when formulated into vaccines, is generally administered in freesolution together with free antigen (WO 96/02555; McCluskie and Davis,supra) or covalently conjugated to an antigen (WO 98/16247), orformulated with a carrier such as aluminium hydroxide ((Hepatitissurface antigen) Davis et al. supra; Brazolot-Millan et al., Proc. Natl.Acad. Sci., USA, 1998, 95(26), 15553-8).

Such immunostimulants as described above may be formulated together withcarriers, such as for example liposomes, oil in water emulsions, and ormetallic salts, including aluminium salts (such as aluminium hydroxide).For example, 3D-MPL may be formulated with aluminium hydroxide (EP 0 689454) or oil in water emulsions (WO 95/17210); QS21 may be advantageouslyformulated with cholesterol containing liposomes (WO 96/33739), oil inwater emulsions (WO 95/17210) or alum (WO 98/15287); CpG may beformulated with alum (Davis et al. supra; Brazolot-Millan supra) or withother cationic carriers.

Combinations of immunostimulants are also preferred, in particular acombination of a monophosphoryl lipid A and a saponin derivative (WO94/00153; WO 95/17210; WO 96/33739; WO 98/56414; WO 99/12565; WO99/11241), more particularly the combination of QS21 and 3D-MPL asdisclosed in WO 94/00153. Alternatively, a combination of CpG plus asaponin such as QS21 also forms a potent adjuvant for use in the presentinvention.

Alternatively the saponin may be formulated in a liposome or in anIscorn and combined with an immunostimulatory oligonucleotide.

Thus, suitable adjuvant systems include, for example, a combination ofmonophosphoryl lipid A, preferably 3D-MPL, together with an aluminiumsalt.

Thus is one embodiment the adjuvant is a combination of QS21 and 3D-MPLin an oil in water or liposomal formulation.

An enhanced system involves the combination of a monophosphoryl lipid Aand a saponin derivative particularly the combination of QS21 and 3D-MPLas disclosed in WO 94/00153, or a less reactogenic composition where theQS21 is quenched in cholesterol containing liposomes (DQ) as disclosedin WO 96/33739. This combination may additionally comprise animmunostimulatory oligonucleotide.

A particularly potent adjuvant formulation involving QS21, 3D-MPL &tocopherol in an oil in water emulsion is described in WO 95/17210 andis another preferred formulation for use in the invention.

Another preferred formulation comprises a CpG oligonucleotide alone ortogether with an aluminium salt.

In a further aspect of the present invention there is provided a methodof manufacture of a vaccine formulation as herein described, wherein themethod comprises admixing a polypeptide according to the invention witha suitable adjuvant.

Particularly suitable adjuvant combinations for use in the formulationsaccording to the invention are as follows:

i) 3D-MPL+QS21 in a liposome

ii) Alum+3D-MPL

iii) Alum+QS21 in a liposome+3D-MPL

iv) Alum+CpG

v) 3D-MPL+QS21+oil in water emulsion

vi) CpG

As used herein, the term “comprising” in context of the presentspecification should be interpreted as “including”.

Embodiments and preferences may be combined as technically appropriate.

The disclosure herein describes embodiments comprising certain integers.The disclosure also extends to the same embodiments consisting orconsisting essentially of said integers.

FIGURES

FIG. 1-10 shows various antibody and fragment sequences

FIG. 11 shows sera titres for TcdA and TcdB

FIG. 12 shows anti TcdA (Ribotype 003) in-vitro neutralization data forsingle Mabs

FIG. 13 shows anti TcdA (Ribotype 003) in-vitro neutralization data forsingle and paired Mabs

FIG. 14-15 shows anti TcdA (Ribotype 003) in-vitro neutralization datafor paired Mabs

FIG. 16-18 shows anti TcdA (Ribotype 003) in-vitro neutralization datafor three Mab mixtures

FIG. 19-20 shows anti TcdA (Ribotype 003) in-vitro neutralization datafor four and five Mab mixtures

FIG. 21-22 shows anti TcdA (Ribotype 003) in-vitro neutralization datafor single and paired Mabs at different TcdA concentrations

FIG. 23-24 shows anti TcdA (Ribotype 003) in-vitro neutralization datafor single and to five Mab mixtures at different TcdA concentrations

FIG. 25-26 shows anti TcdB (Ribotype 003) in-vitro neutralization datafor single Mabs

FIG. 27-30 shows anti TcdB (Ribotype 003) in-vitro neutralization datafor paired Mabs

FIG. 31-33 shows anti TcdB (Ribotype 003) in-vitro neutralization datafor three Mab mixtures

FIG. 34-40 shows anti TcdB (Ribotype 003) in-vitro neutralization datafor two Mab mixtures at different toxin concentrations

FIG. 41-45 shows anti TcdB (Ribotype 003) in-vitro neutralization datafor two Mab mixtures at different relative Mab ratios and differenttoxin concentrations

FIG. 46-59 shows TcdB neutralisation data for single antibodies andpairs of antibodies

FIG. 60 shows the amino acid sequence for TcdA

FIG. 61 shows the amino acid sequence for TcdB

FIG. 62 shows TEER assay data for TcdA in a histogram format

FIG. 62A shows TEER assay data for TcdA in line graph format

FIG. 63 shows a meier-kaplan curve for the combination of antibodies997, 1125 and 1151, high concentration is 50 mg/Kg and low concentrationis 5 mg/Kg 50 mg/kg′ dose gave 100% protection to day 11, ˜82%protection to day 28. 5 mg/kg′ dose resulted in non-durable andincomplete protection.

FIG. 64 shows bodyweight changes for vancomycin and vehicle treatedhamsters

FIG. 65 shows the bodyweight for low dose antibodies 5 mg/Kg and highdose antibodies 50 mg/Kg

FIG. 66 shows photographs of a colon where the animal received treatmentwith antibodies according to the present disclosure vs a control

FIG. 67-68 show effects of vortexing on antibody stability

FIG. 69 shows a comparison of aggregation stability for variousantibodies

FIG. 70-73 show neutralisation of TcdA for various ribotypes

EXAMPLES Antibody Generation

A range of different immunogens and screening reagents were eitherpurchased or produced by conventional E. coli expression techniques inorder to provide a diverse and broad immune response and to facilitateidentification and characterisation of monoclonal antibodies (listed inTable 1). In cases where recombinant proteins or peptides weregenerated, sequences were based on ribotype 027. The sequence for TcdAfrom ribotype 027 is given in SEQ ID NO: 171 (Uniprot accession numberC9YJ37) and the sequence for TcdB from ribotype 027 is given is SEQ IDNO: 172 (Uniprot accession number C9YJ35).

Sprague Dawley rats and half-lop rabbits were immunised with eithersynthetic peptides mapping to regions common to both TcdA and TdcdBfull-length toxin, formaldehyde-inactivated toxoid A, binding domainfragments of Toxin A (CROPs1,2,3 or CROPs4,5,6) or binding domainfragment of Toxin B (CROPs1,2,3,4), or in some cases, a combination ofthe above. Following 2 to 6 immunisations, animals were sacrificed andPBMC, spleen and bone marrow harvested. Sera were monitored for bindingto Toxin A domains, toxin B domains, toxin or toxoid by ELISA. Seratitres of 2 such immunisations are shown in FIG. 11. UCB SLAM was usedas a means to generate monoclonal antibodies. B cells were cultureddirectly from immunised animals (Zubler et al., 1985). This step enabledsampling of a large percentage of the B cell repertoire. Byincorporating the selected lymphocyte antibody method (SLAM) (Babcook etal., 1996) it was possible to deconvolute positive culture wells andidentify antigen-specific antibody-secreting cells. Here we used amodified version of SLAM (UCB SLAM (Tickle et al. 2009)) that utilises afluorescence-based method to identify antigen-specific B cells fromculture wells. B cell cultures were set up and supernatants were firstscreened for their ability to bind a relevant purified toxin domain(binding, translocation or catalytic) in a bead-based assay using anApplied Biosystem 8200 cellular detection system. This was a homogeneousassay using B cell culture supernatant containing IgG, biotinylatedtoxin domains coated onto streptavidin beads and a goat anti-rat/rabbitFc-Cy5 conjugate. Cell cultures positive for binding to TcdA or TcdBcomponents from this assay were selected for use in cell-basedfunctional assays to identify neutralisers of toxin-inducedcytotoxicity. Approximately 12,000 toxin-specific positives wereidentified in the primary binding screen from a total of 40×50-plateexperiments. This equated to the screening of approximately 0.5 billionB cells. Heavy and light variable region gene pairs were isolated fromsingle cells harvested by micromanipulation from approximately 100toxin-neutralising wells following reverse transcription (RT)-PCR. TheseV-region genes were then cloned as mouse IgG1/kappa full-lengthantibodies for rat variable regions and rabbit IgG/kappa full-lengthantibodies for rabbit variable regions. Antibodies were re-expressed ina HEK-293 transient expression system. These recombinant antibodies werethen retested for their ability to neutralise toxin in cell basedassays. Recombinant antibodies were also screened by BIAcore todetermine affinity for a given toxin domain and to also determine thespecificity and approximate the number of binding events of antibody totoxin. Based on in vitro activity in cell based assays and affinitymeasurements, lead candidates were selected for humanisation. Unlessotherwise stated, all the data herein was generated using the humanisedantibodies.

A panel of recombinant, E. coli-produced toxin fragments (TcdA), C.difficile-derived toxin or toxoid (A) and synthetic peptides (B) weregenerated or purchased from commercial sources.

TABLE 1 Toxin A (TcdA) sequence related reagents for screening andimmunizations. Fragment Residue number Source TcdA catalytic M1-E659 UCBE. coli expression TcdA translocation K577-D1350 UCB E. coli expressionTcdA CROPS₁₂₃ (TcdA123) S1827-D2249 UCB E. coli expression TcdA CROPS₄₅₆(TcdA456) G2205-R2608 UCB E. coli expression TcdA CROP₁ S1827-N1978 UCBE. coli expression TcdA CROP₂ G1966-N2133 UCB E. coli expression TcdACROP₃ G2100-D2249 UCB E. coli expression TcdA CROP₄ G2213-N2381 UCB E.coli expression TcdA CROP₅ G2328-N2494 UCB E. coli expression TcdA CROP₆G2462-N2609 UCB E. coli expression TcdA CROP₇ R2554-D2701 UCB E. coliexpression TcdB catalytic M1-A593 UCB E. coli expression TcdBtranslocation R576-D1349 UCB E. coli expression TcdB binding (TcdB1234)S1833-E2366 UCB E. coli expression TcdB CROP₁ S1833-S1981 UCB E. coliexpression TcdB CROP₂ G1968-D2113 UCB E. coli expression TcdB CROP₃G2100-E2247 UCB E. coli expression TcdB CROP₄ G2234-E2366 UCB E. coliexpression Toxin A Full length purchased Toxin B Full length purchasedToxoid A Full length purchased

TABLE 2 Toxin B (TcdB) sequence related reagents forscreening and immunizations. Toxin Domain Amino acid Sequence CatalyticSPVEKNLHFVWIGGEVSD SEQ ID NO: 173 Catalytic NLAAASDIVRL SEQ ID NO: 174Catalytic CGGVYLDVDMLPGIH SEQ ID NO: 175 CatalyticCGGVYLDVDMLPGIHSDLFK SEQ ID NO: 176 CatalyticCWEMIKLEAIMKYK SEQ ID NO: 177 Catalytic CTNLVIEQVKNR SEQ ID NO: 178Catalytic PEARSTISLSGP SEQ ID NO: 179 CatalyticCSNLIVKQIENR SEQ ID NO: 180 Catalytic TEQEINSLWSFDQA SEQ ID NO: 181Catalytic TEQEINSLWSFDPEARSTISLSGPC SEQ ID NO: 182 TranslocationNVEETYPGKLLLC SEQ ID NO: 183 TranslocationAcetyl-CANQYEVRINSEGR SEQ ID NO: 184 TranslocationVNTLNAAFFIQSLIC SEQ ID NO: 185 TranslocationYAQLFSTGLNTIC SEQ ID NO: 186 TranslocationCAGISAGIPSLVNNEL SEQ ID NO: 187 TranslocationDDLVISEIDFNNNSIC SEQ ID NO: 188 Translocation MEGGSGHTVT SEQ ID NO: 189Translocation AVNDTINVLPTITEGIPIVSTILDGINLGAAIK EL SEQ ID NO: 190Binding CGFEYFAPANTDANNIEGQA SEQ ID NO: 191 BindingCGYKYFAPANTVNDNIYGQA SEQ ID NO: 192 Binding CKYYFNTNTAEA SEQ ID NO: 193Binding CKYYFDEDTAEA SEQ ID NO: 194Expression and Purification of C. difficile Anti-Toxin Mabs

Separate light chain and heavy chain mammalian expression plasmids werecombined in equimolar ratios and used to transfect HEK-293 or CHO-Scells. For small scale expression studies lipofectamine and HEK-293cells were used whereas for production of larger batches of IgGelectroporation into CHO-S was preferred.

Culture supernatants were loaded onto a Mab Select SuRe column (in PBSpH 7.4). Antibody was eluted with 100% 0.1M Sodium Citrate pH 3.4buffer. Samples were neutralized to pH7.4 with Tris.Cl pH8.0. Aggregatewas removed by Superdex 200 Gel Filtration column in PBS pH 7.4.

TABLE 3 Cell Volume of Expression Amount Antibody type SN (L) typepurified (mg) CA164_00997.g1_P3 CHO 10 Transient 755.93CA164_00922.g1_P3 CHO 0.5 Transient 129.36 CA164_01125.g2_P3 CHO 10Transient 498.96 CA164_01151.g4_P3 CHO 5 Transient 262.43

Example 1 In-Vitro Neutralization of TcdA Activity by Purified Mabs

All neutralisation screening assays were run in 96 well polystyreneplates. The assay uses CACO-2 cells grown, and screened in MEM+20% FCS,2 mM Q, and NEAA. Any antibody combinations are at equal molar ratiosunless stated otherwise. Day 1: Cells were plated @ 3000 per well in 50μl media, and incubated for 24 hrs; Day 2: Purified samples of humanisedMab were added to 96 well round bottomed polypropylene sterile plates;Spike PP plates with toxin A at a concentration sufficient to generatedthe appropriate lethal dose i.e. LD₈₀ or above and incubate for 1 hr, at37° C.; Add 50 μl of this mixture to cell plates and incubate for 96hrs; Day 5: Add Methylene blue (0.5% Methylene Blue 50% ethanol);Incubate for 1 hr at room temperature; Lyse the cells with 1% N-LaurylSarcosine, and Read on the BIOTEK Synergy2 plate reader at 405 nm. Theresults are shown in FIGS. 12 to 24. EC₅₀ and % maximum neutralizationof TcdA activity shown confirm that the selected antibodies have veryhigh potencies as single agents. Combinations of 2 to 5 of these did notimprove upon the best EC₅₀ or % maximum neutralization. Lack of anysynergy when combining Mabs CA922, 923, 995, 997 and 1000 is animportant observation and may be due to the fact the each antibody alonehas exceptionally high levels of affinity and potency. Supporting datain Example 5 also show that some of the Mabs (e.g. CA997) are capable ofbinding to TcdA subdomains many times. Hence it seems probable thatthese 5 Mabs represent that the maximum affinity, potency and valencythat is achievable when targeting the C-terminal cell binding domain ofTcdA. The antibodies were also effective at neutralising very high toxinconcentrations ranging from LD80 to greater than LD₉₅ (LD_(max)) butsome modest increases in EC₅₀ (i.e. decreases in potency) were observedwith very high levels of [TcdA]. These data are also surprising sinceothers have shown substantial reductions in potency when testingelevated TcdA concentrations (20).

The high potency and affinity of the Mabs described here, e.g. forCA997; is not due solely to their high valency of binding. Others (20and WO06/071877) describe anti-TcdA Mabs capable of binding up to 14times. These Mabs only had affinities in the range 0.3 to 100 nM andshowed incomplete protection against TcdA mediated cell killing, alone(26-63% protection) or in pairs (31-73% protection). Hence it has beendemon-strated that high valency of binding to TcdA does not necessarilyinvoke either high affinity of binding to or neutralisation of TcdA.Neither the affinities nor valency of binding to TcdA were described forMab CDA-1 (18 and U.S. Pat. No. 7,625,559). Thus Mabs described hereinto have surprising affinity, potency and valency.

TABLE 4 Anti TcdA 1, 2 & 3 Mab combinations at a single TcdA conc.(LD₈₀) Final (highest) EC₅₀ Antibody Mab conc.ng/ml (ng/ml) 922 500 1.21923 500 160.42 995 500 37.64 997 500 6.25 1000 500 19.73 922 + 923 5003.58 922 + 925 500 3.326 922 + 997 500 2.88 922 + 1000 500 2.64 923 +995 500 60.23 923 + 997 500 7.54 923 + 1000 500 9.24 995 + 997 500 7.29995 + 1000 500 19.63 997 + 1000 500 4.46 922 + 923 + 995 500 4.72 922 +923 + 997 500 3.23 922 + 923 + 1000 500 3.21 922 + 995 + 997 500 2.22922 + 995 + 1000 500 2.85 922 + 997 + 1000 500 2.22 923 + 995 + 997 5005.04 923 + 995 + 1000 500 9.49 995 + 997 + 1000 500 5.84 922 + 923 +995 + 997 500 2.75 922 + 923 + 995 + 1000 500 3.75 922 + 995 + 997 +1000 500 3.46 923 + 995 + 997 + 1000 500 4.81 922 + 923 + 997 + 1000 5003.06 922 + 923 + 995 + 997 + 1000 500 4.72

TABLE 5 Anti TcdA single, paired, and triplet Mab combinations atvarious TcdA concentrations, where TcdA is at its LD₈₀, LD₉₀, LD₉₅ andLD_(max). Final Mab EC₅₀ Toxin TcdA Sample conc.ng/ml (ng/ml) @ 3000pg/ml 922 500 4.89 (LD_(MAX)) 997 500 10.99 1000 500 50.17 922 + 997 5007.18 922 + 1000 500 6.99 997 + 1000 500 9.437 922 + 997 + 1000 500 10.80922 + 997 + 1000 + 995 500 15.03 922 + 997 + 1000 + 995 + 923 500 7.16 @1000 pg/ml 922 500 1.24 (LD₉₅) 997 500 3.42 1000 500 9.60 922 + 997 5001.85 922 + 1000 500 2.51 997 + 1000 500 3.61 922 + 997 + 1000 500 2.40922 + 997 + 1000 + 995 500 2.74 922 + 997 + 1000 + 995 + 923 500 2.38 @700 pg/ml 922 500 0.84 (LD₉₀) 997 500 2.40 1000 500 6.23 922 + 997 5001.19 922 + 1000 500 1.33 997 + 1000 500 2.68 922 + 997 + 1000 500 1.84922 + 997 + 1000 + 995 500 2.17 922 + 997 + 1000 + 995 + 923 500 2.06 @350 pg/ml 922 500 0.39 (LD₈₀) 997 500 1.18 1000 500 2.76 922 + 997 5000.67 922 + 1000 500 0.85 997 + 1000 500 2.06 922 + 997 + 1000 500 0.83922 + 997 + 1000 + 995 500 0.97 922 + 997 + 1000 + 995 + 923 500 0.98

Example 2 Anti TcdB In-Vitro Neutralization by Purified Mab AssayMethods Description:

All neutralisation screening assays were run in 96 well polystyreneplates.

The assay uses CACO-2 cells grown, and screened in MEM+20% FCS, 2 mM Q,and NEAA. Unless stated all Ab combinations are in equal ratios.

-   -   Day 1: Cells are plated @ 3000 per well in 50 μl media, and        incubated for 24 hrs    -   Day 2: Purified samples of humanised Mab were added to 96 well        round bottomed polypropylene sterile plates    -   Spike PP plates with toxin B lot #031 and incubate for 1 hr, at        37° C.    -   Add 50 μl of this mixture to cell plates    -   Incubate for 96 hrs    -   Day 5: Add Methylene blue (0.5% Methylene Blue 50% ethanol)    -   Incubate for 1 hr at room temperature    -   Lyse the cells with 1% N-Lauryl Sarcosine    -   Read on the BIOTEK Synergy2 plate reader at 405 nm

The data in FIGS. 25 to 33 show that single Mabs alone were relativelyineffective at neutralizing TcdB, both in terms of % maximumneutralization and activity (EC₅₀). However, when the antibodies werecombined in two's and three's considerable improvements in both %maximum neutralization and activity (EC₅₀) were observed. 1125 and 1151were selected as a best pairing, although other good pairings wereobserved: 1125+1153, 1125+1134.

The most effective pairs of Mabs were selected empirically and werefound retrospectively to make unexpected and surprising combinationswhen regarding the individual potencies of each Mab. For example, inTable 6 only CA927 had a TcdB neutralisation potential which couldresult in a defined EC₅₀ whilst the TcdB neutralisation potential ofboth CA1125 and CA1151 were insufficient under these assay conditions toresult in a defined EC₅₀. However, CA927 was not found to be the mosteffective Mab to use within a combination. The best CA927 containingcombination had an EC₅₀ of 13.5 ng/ml whereas other two Mab combinationshad EC₅₀'s as low as 2.59 and 4.71 ng/ml. In another example, in Table 8CA1099 had the lowest TcdB neutralisation EC₅₀ under the assayconditions used. However, CA1099 was not found to be the most effectiveMab to use within a combination. The best CA1099 containing combinationhad an EC₅₀ of Eng/ml whereas other two Mab combinations had EC₅₀'s aslow as 2 and 1 ng/ml. We might speculate that the most effectivepairings of Mabs are defined by their cooperative binding modalitiesespecially as defined by having non-overlapping epitopes.

TABLE 6 Anti-TcdB Mab combinations and relative Mab ratios at constanttoxin concentration. Final Mab Sample conc.ng/ml EC₅₀(ng/ml) 1125.g21000 >1000 1134.g5 1000 >1000  927.g2 1000 12.89 1153.g8 1000 >10001102.g4 1000 >1000  927 + 1099 1000 >1000  927 + 1102 1000 >1000  927 +1114 1000 >111.111  927 + 1125 1000 13.55  927 + 1134 1000 51.58 1099 +1114 1000 >1000 1102 + 1114 1000 >333.333 1102 + 1125 1000 15.51 1114 +1134 1000 19.70 1114 + 1151 1000 25.69 1114 + 1153 1000 27.48 1125 +1134 1000 2.59 1125 + 1151 1000 4.71 1125 + 1153 1000 21.23 1125 +1134 + 1114 1000 3.77 1125 + 1134 + 927  1000 2.63 1125 + 1151 + 11141000 4.90 1125 + 1151 + 927  1000 5.69 1125.g2 + 1134.g5 + 927.g2  10005.83 1125.g2 + 1134.g5 + 1153.g8 1000 9.89 1125.g2 + 1134.g5 + 1102.g41000 2.72

Example 3 Neutralisation of TcdB by Combinations of Purified Mab

All neutralisation screening assays were run in 96 well polystyreneplates.

The assay uses CACO-2 cells grown, and screened in MEM+20% FCS, 2 mM Q,and NEAA.

-   -   Day 1: Cells are plated @ 3000 per well in 50 μl media, and        incubated for 24 hrs    -   Day 2: Purified samples of humanised Mab were added to 96 well        round bottomed polypropylene sterile plates    -   Spike PP plates with toxin B (VPI 10463) and incubate for 1 hr,        at 37° C.    -   Add 50 μl of this mixture to cell plates    -   Incubate for 72 hrs    -   Day 5: Add Methylene blue (0.5% Methylene Blue 50% ETOH)    -   Incubate for 1 hr at room temperature    -   Lyse the cells with 1% N-Lauryl Sarcosine    -   Read on the BIOTEK Synergy2 plate reader at 405 nm

The results are shown in FIGS. 34 to 45.

These data show that the best pair of Mabs for neutralizing TcdB at arange of toxin concentrations was CA1125 and CA1151. Moreover, the1125+1151 combination was largely unaffected by changes in the relativemolar ratios which is in contrast to 1125+1153.

TABLE 7 Anti-TcdB Mab combinations and relative Mab ratios at 3different toxin cones. EC50 values (ng/ml) Antibody combination TcdBLD60 TcdB LD77 TcdB LD85 1125.g2 + 927.g2 (50:50)  2.8 6 11.3 1125.g2 +1102.g4 (50:50) 4 13 44 1125.g2 + 1114.g8 (50:50) 3.5 7.1 25.4 1125.g2 +1134.g5 (50:50) 0.48 1.4 4 1125.g2 + 1151.g4 (50:50) 0.85 0.85 1.51125.g2 + 1153.g8 (50:50) 2.7 5.2 25.2 1125.g2 + 1134.g5 (25:75) <0.150.84 7.2 1125.g2 + 1151.g4 (25:75) 0.73 1 2.1 1125.g2 + 1153.g8 (25:75)7 10 27 1125.g2 + 1134.g5 (75:25) 0.66 1.2 2.5 1125.g2 + 1151.g4 (75:25)1.4 1.2 8.3 1125.g2 + 1153.g8 (75:25) 2.9 7.5 30

The data show that even the most active specific paired combinationshave surprisingly and non-predictably different properties relative toeach other. The EC₅₀ of the preferred combination of CA1125 and CA1151in equimolar ratios is largely unaffected by an increasing [TcdB]. Thethree relative molar ratios of Mabs tested (i.e. 25:75 vs 50:50 vs75:25) have very similar EC₅₀'s to each other, suggesting that CA1125and CA1151 have especially complementary modes of action. This is incontrast to the combination of CA1125 with CA1134 where the increase inEC₅₀ (i.e. reduction of potency) with higher [TcdB] is more substantialand where the three Mab molar ratios are not equally effective: TheCA1125:CA1134 ratio of 25:75 is notably less potent than 50:50 and75:25. This suggests that the combined potency of CA1125+CA1134 is moredependent upon the CA1125 component. The EC₅₀ of all three molarcombinations of CA1125 and CA1153 is substantially affected byincreasing [TcdB] suggesting that CA1153 is a less suitable partner forcombination with CA1125. In toto, these data show that CA1125 and CA1151are a particularly favourable combination since the highest potency ismaintained across a range of Mab and TcdB molar ratios.

TABLE 8 TcdB neutralisation - 1 or 2 anti-TcdB Mabs at constant toxindose (LD₈₀). Antibody IC50 (ng/ml) 1099 2 1102 N/A 1114 103 1125 N/A1134 8 1151 182 1153 260 926 N/A 927 N/A 1099 + 1125 6 1114 + 1125 71151 + 1125 2 1134 + 1125 1 1102 + 1125 6 1125 + 1153 12  926 + 1125 42 927 + 1125 4

TABLE 9 TcdB neutralisation - 1 or 2 anti-TcdB Mabs at various TcdBdoses. EC50 values (ng/ml) Maximum neutralisation Antibody combinationTcdB LD75 TcdB LD86 TcdB LD90 TcdB LD75 TcdB LD86 TcdB LD90 1125.g2 n/an/a n/a 40% 25% 15% 1114.g8 n/a n/a n/a 45% 25% 15% 1134.g5 n/a n/a n/a45% 25% 15% 1151.g4 n/a n/a n/a 45% 25% 20% 1153.g8 28.3 n/a n/a 65% 35%28% 1125.g2 + 1114.g8 (50:50) 10.1 243.8 n/a 85% 65% 40% 1125.g2 +1134.g5 (50:50) 1.7 22.6 n/a 87% 60% 40% 1125.g2 + 1153.g8 (50:50) 6.132.2 n/a 95% 75% 48% 1125.g2 + 1151.g4 (50:50) 0.8 2.8 19.1 85% 80% 55%1125.g2 + 1151.g4 (25:75) 1.2 2.8 47.2 85% 75% 60% 1125.g2 + 1151.g4(75:25) 2.9 3.8 2.6 75% 70% 60%

These data show that combination of Mabs, especially CA1125 and CA1151improve both the potency as measured by EC₅₀ but also as measured by %maximum protection. The % maximum protection is of particular relevancein this assay method since the Mab:TcdB mixture is incubated with cellsfor a long time (72 h). Since TcdB is toxic to Caco-2 cells in the rangeof pg/ml in 2-4 h this measure may be considered to be a very difficulttest of Mab neutralisation ability and may reflect the ability of Mabmixture with regard to their binding kinetics or modalities. In turnthis may reflect the ability of Mab mixtures to protect against theeffects of TcdB during an established infection when there may besubstantial quantities of TcdB within tissues for many hours. Selecteddata from Tables 6-9 are further illustrated in FIGS. 46-59.

Example 4 Valency of Binding of Mabs to TcdB Sub-Domains

The number of moles of binding events of anti-C. difficile TcdBantibodies to TcdB₁₂₃₄ was determined by Surface Plasmon Resonance (SPR)on a Biacore 3000 (GE Healthcare). Streptavidin was immobilized on a CM5sensor chip (GE Healthcare) to a level of ˜4000RU via amine coupling andbiotinylated TcdB₁₂₃₄ was bound at 500-600RU. Two 20 μl injections ofthe same anti-TcdB antibody mixtures (final concentration of eachantibody was 500 nM) were injected over this surface at 10 μl/min andthe saturating binding response recorded. The surface was regeneratedafter every cycle using HCl. All the data was corrected for backgroundbinding using the response to the streptavidin only reference flowcell.

TABLE 10 Surface plasmon resonance analysis of the number of IgG bindingsites on TcdB₁₂₃₄ No. of Binding Binding relative Antibody bindingResponse to CA927 combination cycle repeats (RU) average responseCA1125.g2 10 750 0.9 CA1151.g4 10 1232 1.6 CA1125_CA1151 4 1941 2.5CA1125_CA927 3 1570 2.0 CA1151_CA927 3 1959 2.5 CA927 8 791 1.0

All responses have been expressed relative to a multiple of CA927average response (final column table 10) since CA927 appears to berepresentative of a Mab which binds to TcdB₁₂₃₄ once only.

Immobilized CA1125, when bound to TcdB₁₂₃₄, does not allow CA1125 tobind further supporting the idea that CA1125 has one binding site onTcdB₁₂₃₄ and that after this has been saturated that no other bindingsite for CA1125 can be found. However, when TcdB₁₂₃₄ has been saturatedby CA1125, CA1151 can still bind. This demonstrates that CA1151 binds atalternative sites to that occupied by CA1125. Together these data showthat CA1125 is a single binder of TcdB₁₂₃₄ whereas 1151 IgG binds toTcdB₁₂₃₄ more than once, most likely twice. Hence a mixture of CA1125and CA1151 can bind to TcdB₁₂₃₄ approximately 3 times.

All antibodies combinations have an additive binding response showingthat there are 2 or more non-competitive sites on TcdB₁₂₃₄ bound bythese combinations.

Example 5 Valency of Binding of Mabs to TcdA Sub-Domains

The number of moles of binding events of anti-C. difficile TcdAantibodies to TcdA₁₂₃ and A₄₅₆ were determined by Surface PlasmonResonance (SPR) on a Biacore 3000 (GE Healthcare). Streptavidin wasimmobilized on a CM5 sensor chip (GE Healthcare) via amine coupling to alevel of ˜4000RU and biotinylated TcdA₁₂₃ was bound to one flowcell andTcdA₄₅₆ was bound to a different flowcell to a response of ˜500RU. Two30 μl injections of the same anti-TcdA antibody at 1 μM were injectedover both flowcells at 10 μl/min and the saturating binding responserecorded. The surface was regenerated after every cycle using HCl. Allthe data was corrected for background binding using the response to thestreptavidin only reference flowcell.

TABLE 11 SPR analysis of the binding responses of IgGs to immobilisedTcdA₁₂₃ and TcdA₄₅₆ CA997 CA1000 CA997/CA1000 ratio TcdA123 1069 166 6TcdA456 1285 407 3

Antibodies CA997 and CA1000 bind to TcdA₁₂₃ in a ratio of six CA997's toone CA1000 whereas they bind to TcdA₄₅₆ in a ratio of three CA997's toone CA1000 (Table 2).

The maximum antibody response for CA997, corrected for molecular weightand immobilized toxin level is similar for TcdA₁₂₃ and TcdA₄₅₆. Thissuggests that CA997 binds TcdA₄₅₆ six times and CA1000 binds twice toTcdA₄₅₆. Hence antibody CA997 likely binds to TcdA whole toxin (TcdA)approximately 12 times.

Overall CA997 binds six times or more to A₁₂₃ and six times or more toA₄₅₆, whereas CA1000 binds at least once to A₁₂₃ and twice to A₄₅₆.

Increased valency of binding to TcdA and TcdB may have two importanteffects in vivo. The first is that any Mab or Mab mixture which iscapable of binding TcdB more than once will have increased potential toform inter-toxin binding events and hence immunoprecipitation.Immunoprecipitation can contribute to potency by reducing the solubilityof toxin and forming very large macromolecular complexes which hencereduce the effective working concentration of toxin. Such large proteincomplexes may be taken up by macrophages and monocytes resident in thetissue and may contribute to an augmented host immune response.Antigen:antibody complexes bearing Fc fragments have been specificallyshown to be capable of priming a host immune response against a gutpathogen (21). Also, soluble antigen:antibody complexes have beensuccessfully used as a vaccine directed against the antigen in humanclinical trials (22). In addition, immune decoration of toxin with Fcbearing IgG may contribute to immune clearance using normal mechanismsthrough the liver and spleen. In general, higher levels of Fc decorationof antigen lead to faster and more complete levels of clearance (23)Critically, it may be that presence of 2 or more Mab Fc domains pertoxin, especially 3 Fc domains per toxin may represent a critical numberof Fcs required for very rapid and substantial clearance of toxin (24).The anti-TcdA Mab CA997 is likely capable of binding to TcdA up to 12times and the combination of CA1125 and CA1151 is likely capable ofbinding to TcdB 3 times. Hence the 3 Mab mixture is very likely to becapable of providing for these kinds of additional potency mechanisms invivo.

Example 6 Mab Neutralisation of Loss of TEER Caused by TcdA

C. difficile monolayer integrity assay is performed using theBecton-Dickinson (BD) Caco-2 BioCoat HTS plate system.

Day 1—Caco-2 cells seeded @ 2×10⁵/ml per well of the plate insert in 500μl Basal seeding medium (provided by BD). 35 ml of Basal seeding mediumadded to the feeder tray. Cells incubated for 24 hours at 37° C. Day2—Basal seeding medium removed from inserts and feeder tray, andreplaced with Entero-STIM differentiation medium (supplied by BD). 500μl added per well insert and 35 ml to the feeder tray. Cells incubatefor a further 72 hrs at 37° C. Day 5—Antibodies prepared at 2×concentration relative to that to be used in the assay well in apolypropylene plate and toxin A. Toxin A added to antibodies at aconcentration of 125 ng/ml and plate incubated for 1 hr at 37° C. 1 mlof Caco-2 growth medium (MEM+20% FCS, 2 mM Q, NEAA) added to each wellof a standard 24-well TC plate. BioCoat insert plate transferred to the24-well TC plate. Entero-STIM medium removed from inserts and replacedwith 400 μl of toxin:Ab mixture. Loss of tight junctions between gutcells is the key early effect of TcdA on cell monolayers and gut tissuesections and is the primary cause of diarrhoea. Albumin and other serumproteins are lost into the gut lumen along with accompanying serumfluid. The loss of trans-epithelial electrical resistance indifferentiated cultured cells which have formed a monolayer is a usefulsurrogate for the protection against the acute effects of TcdA. Threeantibodies shown have good levels of protection against TEER loss, FIG.62. It is notable and surprising that the abilities of these Mabs inTEER assays do not reflect those seen in toxin neutralization asmeasured in a cell proliferation assay. CA922 has the best performancein a cell proliferation assay (EC₅₀=1.21 ng/ml) and yet this isconsiderably out-performed in the TEER assay by an antibody (CA1000)which has >10× lower potency in a cell proliferation assay (EC₅₀=19.73ng/ml). CA997 had the best performance in the TEER assay since it hadboth high levels of protection and maintained this at the lower Mabconcs. CA997 had a substantial potential to neutralize TEER loss withmaximal inhibition approaching 80% and an EC₅₀ of approximately 80 ng/mlat 4 h. These observations are unexpected since the Mabs in question allhad high affinities for TcdA domains (CA922 ˜4 pM, CA997 ˜132 pM, CA1000˜73 pM). These data suggest that CA997 and CA1000 recognise epitopesimportant in TEER loss or neutralize TcdA by different mechanism toother Mabs. Furthermore, since CA1000 is estimated to bind to holotoxintwice (once in TcdA₁₂₃ and once in TcdA₄₅₆) CA1000 may define ‘TEERcritical’ epitopes within the TcdA cell binding regions which might haveparticular value for defining vaccine immunogens. Results are shown inFIG. 62.

Example 7 Affinity of Anti-C. difficile Toxin Antibodies for Sub-Domainsof TcdA and TcdB: TcdA₁₂₃, TcdA₄₅₆ and TcdB₁₂₃₄

Kinetic constants for the interactions of anti-C. difficile TcdA andTcdB antibodies were determined by surface plasmon resonance conductedon a BIAcore 3000 using CM5 sensor chips. All experiments were performedat 25° C. Affinipure F(ab′)₂ fragment goat anti-human IgG, Fc fragmentspecific (Jackson ImmunoResearch) was immobilised on a CM5 Sensor Chip(GE) via amine coupling chemistry to a capture level of ≈7000 responseunits (RUs). HBS-EP buffer (10 mM HEPES pH 7.4, 0.15 M NaCl, 3 mM EDTA,0.005% Surfactant P20, Biacore AB) was used as the running buffer with aflow rate of 10 μL/min. A 10 μL injection of each antibody at 1 ug/ml orlower was used for capture by the immobilised anti-human IgG, Fc.TcdA123, TcdA456 or TcdB1234 were titrated over captured purifiedantibodies at doubling dilutions from 12.5 nM at a flow rate of 30μL/min. For antibodies present in culture supernatants, a singleconcentration of 12.5 nM of TcdA123 or TcdA456 and 50 nM of TcdB1234 waspassed over the antibodies at 30 ul/min. Kinetics were calculated on n=2The surface was regenerated at a flowrate of 10 uL/min by two 10 μLinjections of 40 mM HCl, and a 5 μL injection of 5 mM NaOH. Doublereferenced background subtracted binding curves were analysed using theBIAevaluation software (version 3.2) following standard procedures.Kinetic parameters were determined from the fitting algorithm.

TABLE 12 Anti-TcdA Mab affinities and binding kinetics Antibody ID ka(1/Ms) kd (1/s) KD (M) KD (pM) Material/Assay TcdA123 CA164_00922.g11.09E+06 4.43E−06 4.06E−12 4.06 Purified Mab 5 point CA164_00923.g15.36E+05 3.47E−05 6.47E−11 64.7 titration CA164_00995.g1 No binding Nobinding CA164_00997.g1 7.84E+05 1.03E−04 1.32E−10 132 CA164_01000.g11.33E+05 9.78E−06 7.33E−11 73.3 CA164_00993.g1 9.00E+05 5.00E−065.56E−12 5.56 Supernatant 2x 1 point titration TcdA456 CA164_00922.g11.29E+06 3.33E−06 2.59E−12 2.59 CA164_00923.g1 6.16E+05 1.92E−043.12E−10 312 Purified Mab 5 point CA164_00995.g1 2.87E+05 3.42E−051.19E−10 119 titration CA164_00997.g1 9.21E+05 6.15E−05 6.68E−11 66.8CA164_01000.g1 3.55E+05 2.98E−05 8.41E−11 84.1 CA164_00993.g1 1.25E+065.00E−06 4.00E−12 4.00 Supernatant 2x 1 point titration

TABLE 13 Anti-TcdB Mab affinities and binding kinetics Antibody ID ka(1/Ms) kd (1/s) KD (M) KD (pM) Material/Assay TcdB1234 CA164_1125.g22.64E+05 3.23E−05 1.22E−10 122 Purified Mab 3 point titrationCA164_1151.g4 7.49E+05 4.13E−04 5.51E−10 551 Purified Mab 3 pointtitration CA164_926.g1 1.38E+05 7.12E−05 5.16E−10 516 Supernatant 2x 1point titration CA164_927.g2 3.97E+05 3.61E−05 9.11E−11 91 Purified Mab3 point titration CA164_1099.g2 5.24E+05 1.63E−05 3.10E−11 31 PurifiedMab 3 point titration CA164_1102.g4 1.17E+05 3.78E−04 3.25E−09 3250Supernatant 2x 1 point titration CA164_1114.g2 2.87E+05 1.97E−036.87E−09 6870 Supernatant 2x 1 point titration CA164_1114.g8 2.55E+051.85E−03 7.25E−09 7250 Supernatant 2x 1 point titration CA164_1129.g11.89E+05 2.30E−04 1.22E−09 1220 Supernatant 2x 1 point titrationCA164_1134.g5 5.09E+05 2.45E−05 4.81E−11 48 Purified Mab 3 pointtitration CA164_1153.g8 1.43E+05 4.48E−05 3.14E−10 314 Purified Mab 3point titration

The anti-TcdA affinities are particularly high compared to the publishedaffinities of other Mabs. We demonstrate that affinities as low as 4 pMare achievable. The preferred CA997 has an affinity of 132 pM, CA1125122 pM and CA115 551 pM. CA995 clearly shows that it does not bind toCROPs A₁₂₃ and hence that demonstrates that the Mab shown here haveproperties which are different from each other in surprising andunexpected ways. CA922, 923, 997 and 1000 do bind at least once to CROPsA123 and A456. Hence these 4 Mabs confirming that each must bind toholotoxin at least twice. We have been unable to derive affinities forthe binding of these Mabs to holotoxin due to technical constraints.However, given the high affinities and valencies demonstrated for theanti-TcdA Mabs it is possible to speculate that the functionalaffinities against holotoxin may be even stronger than those illustratedfor binding to toxin sub-domains. The anti-TcdB Mabs also demonstratedstrong affinities reaching as low as 31 pM. In particular CA1125, 1151,927, 1099, 1134 and 1153 show affinities which surpass thosedemonstrated by others.

Example 8 Biophysical Characterisation of C. difficile Anti-ToxinHumanised IgG1 Molecules Molecules Analysed Anti-TcdA IgG1:CA164_00922.g1 CA164_0923.g1 CA164_0995.g1 CA164_0997.g1 CA164_01000.g1Anti-TcdB IgG1 CA164_01125.g1 CA164_01125.g2 CA164_01134.g4CA164_01134.g5 CA164_01134.g6 CA164_01102.g1 CA164_01102.g4CA164_01151.g4

Antibody combinations need to be made up of Mabs having high levels ofstability in order to mitigate potential risks of aggregation duringlong term storage. Thermal stability (Tm) is used as one measure. Ofspecial value to Mab mixtures is measuring their propensity to aggregatedue to physical stress such as agitation or shaking. Aggregates areundesirable components of drug compositions since they may reducestorage life time and may pose a safety risk to patients at certainlevels. The Tm data show that all 5 anti-TcdA Mabs have high Tmstability, whilst three (CA922, 923 and 997) have very high Tm's in therange of 79-81° C. Of the anti-TcdB Mabs tested all but two have veryhigh Tm's. Of note is that CA997, CA1125 and CA1151 which were tested inthe hamster infection study (Example 9) had very high Tm's (79.2° C.,79.3° C. and 80.8° C. respectively) which makes them suitable for use ina Mab mixture.

In the shaking aggregation assay, CA997 and 922 had the lowestpropensity to aggregate of the 5 anti-TcdA Mabs. Similarly, CA115 and1151 had the lowest aggregation propensities of the anti-TcdB Mabs.Hence the use of CA997, 1125 and 1151 as a Mab mixture may have specialvalue since they are more likely to survive co-formulation and storageat high protein concentrations.

Estimation of Isoelectric Point (pI) by Capillary IEF

Samples were prepared by mixing the following: 30 ul Protein sample at 2mg/ml, 0.35% Methylcellulose, 4% pH3-10 ampholytes (Pharmalyte),synthetic pI markers (4.65 and 9.77), 1 ul of each stock solution, andHPLC grade water to make up the final volume to 200 ul. The mixture wasthen analysed using iCE280 IEF analyzer (pre-focusing at 1500V for 1 minfollowed by focusing at 3000V for 6 mins). The calibratedelectropherograms were then integrated using Empower software (fromWaters)

Thermal Stability (Tm) Measured Via Thermofluor Assay.

This method uses Sypro orange fluorescent dye to monitor the unfoldingprocess of protein domains. The dye binds to exposed hydrophobic regionsthat become exposed as a consequence of unfolding which results in achange to the emission spectrum.

The sample (5 ul at 1 mg/ml) is mixed with a 5 ul of a stock solution ofSypro orange (30×) and the volume made up to 50 ul with PBS, pH 7.40.

10 ul aliquots of this solution is applied towells in a 384 well plate(n=4).

The plate is placed in a 7900HT fast real-time PCR system containing aheating device for accurate temperature control. The temperature isincreased from 20° C. to 99° C. (Ramp rate of 1.1° C./min). A CCD devicesimultaneously monitors the fluorescence changes in the wells. Analgorithm is used to process intensity data and take into accountmultiple transitions.

Stressing of Samples by Agitation.

During manufacture antibody samples are subjected to mechanical stressgenerated by processes such as pumping and filtration. This may causedenaturation and consequently aggregation due to exposure of the proteinto air-liquid interfaces and shear forces resulting in the ultimate lossof bioactivity. Stress by vortexing is a method to screen the robustnessof the antibody samples for prediction of aggregation stability.

Both anti-TcdA and anti-TcdB IgG1 molecules were subjected to stress byagitation, by vortexing using an Eppendorf Thermomixer Comfort at 25°C., 1400 rpm. Sample size was 250 uL, (×3 per sample) in a 1.5 mLconical Eppendorf-style capped tube (plastic), in PBS pH 7.4. Eachsample was brought to a concentration of 1 mg/ml (using extinctioncoefficient calculated from sequence) and aggregation was monitored byabsorbance at 340 nm and/or 595 nm, by use of a Varian Cary 50-Biospectrophotometer, measured at intervals for up to 24 hours.

Results Table 14 provides a summary of the measured pI and Tm data forboth anti-TcdA and anti-TcdB IgG1 molecules.

TABLE 14 Compilation of pI and Tm Data measured Tm(Fab) Anti-TcdA IgG1pI in PBS Tm(CH2) CA164_00922.g1 8.8 81 69.2 CA164_0923.g1 9.2 79 69.3CA164_0995.g1 8.5 71 no data* CA164_0997.g1 8.3 79.2 68.4 CA164_01000.g17.74 70.5 no data* Anti-TcdB IgG1 CA164_01125.g1 9.2 79.3 69.4CA164_01125.g2 9.2 79.5 69.3 CA164_01134.g4 9.3 78.4 69.4 CA164_01134.g59.2 76.4 69.2 CA164_01134.g6 9.2 76.6 69.6 CA164_01102.g1 9.1 69 nodata* CA164_01102.g4 9.1 69.1 no data* CA164_01151.g4 9.2 80.8 69.8*denotes that it was not possible to discern the Fab and CH2 domains.

Measured pI

The measured pI of the molecules were high (except forCA164_01000.g1_P3) and away from the pH of formulation buffers such asPBS, pH 7.4 and 50 m sodium acetate/125 mM sodium chloride, pH 5. Thismay mean that buffers with pH's suitable for co-formulation of two ormore Mabs can be selected.

Thermal Stability (Tm) Measured Via Thermofluor Assay

Since all of the molecules are IgG1, the Tm of the Fc domain (Tm(CH2))are the same. The difference in thermal stability between the moleculescan be determined by the Tm of the Fab′ domain (Tm(Fab)).

For the anti-TcdA molecules, the rank order (most stable first) wasCA922≥997>923>995>1000 and for the anti-TcdB molecules (most stablefirst) was CA1151.g4>1125.g1,g4>1134.g4>1134.g5≥1134.g6>1102.g1=1102.g4.

Stressing of Samples by Agitation It was possible to determine differentaggregation stability between the different antibodies, FIG. 67 showsthe effect of agitation via vortexing on different anti-TcdA IgG1molecules in PBS, pH 7.4.

It was possible to determine a ranking order (most aggregation stablefirst): CA922≥997>923≥995>1000

FIG. 68 shows the effect of agitation via vortexing on differentanti-TcdB molecules.

It was possible to rank the order of aggregation stability, such thatthe CA1125 grafts appeared more stable than the CA1134 molecules whichwere more stable than the CA1102 molecules.

A further study was performed to compare directly the aggregationstability of the anti-TcdB molecule (CA1151.g4) with the more stablemolecule CA1125.g2 (see FIG. 2) and more aggregation stable anti-TcdAmolecules (CA922.g1 and CA997.g1). The results can be seen in FIG. 69.

Further results for these 4 Mabs are also shown in FIGS. 67 and 68.

For the anti-TcdA molecules, CA922.g1 and CA977.g1, CA922 werepreferable based on the analyses above, although apart from CA1000) allmolecules could be considered suitable candidates for use as therapeuticIgG1.

For the anti-TcdB molecules, the biophysical characteristics could begrouped within the family of grafts based on the aggregation stabilityand Tm, such that the CA1125 grafts potentially proved more stable. TheCA1102 grafts showed poorest Tm data and also showed the greatesttendency to aggregate via stress by agitation.

A study using CA1151.g4 showed that this molecule exhibited slightlyincreased aggregation stability relative to CA11125.g2 and seemedequivalent to the TcdA molecules (CA922.g1 and CA997.g1. All fourmolecules showed equivalent Tm values. CA997, CA1125 and CA1151 showvery high levels of thermostability and very low levels of aggregateformation after agitation.

Example 9 Anti-C. difficile Toxin Mab Hamster Infection Study

The hamster infection study was performed by Ricerca Biosciences LLC,Cleveland, Ohio, USA. The study protocol was approved by the RicercaIACUC committee. Active and control components (composition and dose)were blinded to Ricerca staff until after completion of the planned 28day study period.

Golden Syrian male hamsters (weight 82-103 g, 54 days old) wereindividually housed in HEPA filtered disposable cages and fed TekladGlobal Diet 2016 and water ad libitum. After acclimatisation, hamsterswere pre-dosed (i.p.) with Mab mixtures or PBS (vehicle control) once aday for each of 4 days: days −3, −2, −1 and 0. Two doses of Mab wereinvestigated: high dose=50 mg/kg each of anti-TcdA and anti-TcdBcomponents and low dose 5 mg/kg each of anti-TcdA and anti-TcdBcomponents.

The drug combination tested was composed of one anti-TcdA antibody(CA997.g1) which constituted 50% of the injected protein and twoanti-TcdB antibodies (CA1125.g2 and CA1151.g4) which togetherconstituted 50% of the injected protein but which alone constituted 25%of the injected protein. Hamsters were sensitised (day −1) with 50 mg/kgof Clindamycin phosphate in PBS (s.c.) before being challenged 1 daylater (day 0) with 3.4×106 c.f.u. of vegetative cells from strainATCC43596. Vancomycin was dosed at 5 mg/kg twice a day for 5 days (p.o.)on days 1, 2, 3, 4, 5.

Viability checks were performed on animals twice a day, animals found tobe in extremis were euthanised and counted as dead. Body weights weredetermined on each day of dosing, then twice weekly and beforeeuthanising survivors. Gross necropsy was performed on all animals.Survival curves were created by the method of Kaplan and Meier. Survivalcurves were analysed using the P value from the log rank test comparedto the Bonferroni corrected threshold of P=0.005. The Vancomycin treatedgroup were not included in the analysis. All statistical tests were donewith Prism v5.04. All groups contained 11 animals, except the Vancomycincontrol group which contained 5 animals.

Survival curves can be seen in FIG. 63. Hamsters receiving PBS (control)all died on days +2 and +3, whilst those receiving vancomycin treatmentfor 5 days all died on days +10 and +11. Hamsters receiving the highdose of UCB Mab mixture all survived until day +11, thereafter only twoanimals died until the end of the 28 day study. Hamsters receiving thelow dose of UCB Mab mixture all survived until day +3, thereafteranimals were lost fairly steadily until day +16 when all had died. Thedata show exceptional levels and duration of protection when compared topublished data for use of anti-toxin Mabs in hamsters (18). These invivo data support the in vitro observations of very high levelperformance for neutralization and stability.

There is no apparent link between death and body weight during the acutephase (days 1-5) of the infection, FIGS. 64-65. Hence it may be supposedthat hamsters die of overwhelming direct and indirect effects of TcdAand TcdB. Hamsters which survive the acute period due to partialprotection (UCB low dose) of neutralizing Mabs lose weight, presumablydue to gut damage and altered nutritional status. It was notable thatmany of the hamsters which went on to survive the 28 period of the studydue to the protective effects of the UCB high dose Mabs recovered fromweight loss and indeed even gained weight. This may be taken as evidenceof the superior protective effects of the UCB Mabs enabling the gut tofunction as normal.

TABLE 15 Gross pathology scores Anogenital Black Dark red Red PinkNormal staining Red small Group caecum caecum caecum caecum caecum‘wet-tail’ intestine PBS 1 9 1 0 0 1 1 control UCB low 0 4 5 2 0 4 1 UCBhigh 0 0 1 1 9 3 0

It is clear that UCB Mabs were able to protect the large and smallintestines from the bloody effusions caused by TcdA and TcdB.

The results are shown in FIGS. 63 to 66

The photographs in FIG. 66 show typical gross pathologies for theswelling and bloody effusions of caeca caused by TcdA and TcdB (leftimage, PBS control, animal death on day 2) and a normal stool filledcaeca after protection by UCB high dose Mabs (right image, UCB highdose, animal surviving to day 28). These data show that after protectionwith a high dose of UCB Mabs the large intestine can return to normalmorphology and function.

Example 10 Neutralisation of TcdA from Different Ribotyped Strains byPurified Mab

Clinical infections are caused by a variety of different strains. Straindifferences are characterized using a number of different methods ofwhich ribotyping is a key one. Different ribotype strains are observedto have different pathogenicity, infection and sporulation properties.All of the TcdA neutralization shown above used TcdA purified fromstrain known as VPI10463. However, the predominant aggressivelypathogenic strain associated with out-breaks is called ribotype 027.Other key ribotypes include 078, 001, 106. Amino acid sequencedifference have been observed between toxins produced by differentribotypes and hence it is important that Mabs are capable ofneutralizing toxin from a diverse set of clinical isolates. CA922, 997and 1000 were tested for their ability to neutralize TcdA from strains027 and 078 and compared to their abilities against TcdA from VPI10463.Mabs were tested at 4 [TcdA] and found to be capable of neutralizing alltoxins without significant difference at LD₈₀, LD₉₀ and LD₉₅

TABLE 16 EC50 values (ng/ml) - TcdA strain VPI 10463 Antibody LD80 LD90LD95 LDmax CA164_922 0.27 0.9 1.2 >500 CA164_997 1 2.5 3.5 25.4CA164_1000 3.6 13.5 19.3 >500

TABLE 17 EC50 values (ng/ml) - TcdA ribotype 027 Antibody LD80 LD90 LD95LDmax CA164_922 0.19 0.25 0.41 1.46 CA164_997 0.92 1.27 1.75 7.19CA164_1000 2.25 2.49 3.52 16.32

TABLE 18 EC50 values (ng/ml) - TcdA ribotype 078 Antibody LD80 LD90 LD95LDmax CA164_922 0.11 0.12 0.25 0.68 CA164_997 0.33 0.64 1.11 2.57CA164_1000 2.04 2.41 5.03 14.16

Example 11 PK Data

A PK study of a human IgG1 (20 mg/kg) in healthy hamsters. The hamsterPK was found a half-life similar to Mabs in mice or rats. (t½ 6-8 days).i.p. and s.c. dosing were essentially the same. The pharmacokinetics anddistribution to the gut of a hIgG1 Mab was studied in ‘normal’(non-infected) golden Syrian hamsters. Purified Mab was administered tomale hamsters (120-135 g) by CARE Research LLC, Fort Collins, Colo., USAand samples were assayed by UCB Pharma. The study was approved by theCARE IACUC committee. Eight animals each received a single dose of 20mg/kg of IgG1, four were dosed i.p., four were dosed s.c. Blood wascollected at 1, 3, 8, 24, 48, 72, 103 and 168 hours post-dose, serum wasseparated before storage at −80° C. Blood was also taken from twountreated hamsters in order to provide assay controls. Followingeuthanasia, a 2 cm length of colon was cut from the caeca junctiononwards from each hamster. The colon section was flushed with washbuffer (50% (v/v) PBS containing 50% (v/v) Sigma protease inhibitorcocktail (P2714) before being opened and separation and removal of themucosa from the underlying muscle. Mucosal samples were placed in 0.5 mlof wash buffer homogenized until visually uniform and stored at 4° C.before immediate shipping on wet ice. For the anti-human IgG1 ELISA Nuncmaxisorp 96 well plates were coated overnight in 0.1M NaHCO₃ pH 8.3 withGoat F(ab′)2 anti-human IgG-Fcγ fragment (Jackson 109-006-098), plateswere washed with PBS-Tween (PBS/0.1% (v/v) Tween 20) and then blockedwith 1.0% (w/v) BSA & 0.1% (v/v) Tween in PBS. Serum samples werediluted in sample-conjugate buffer (1% (w/v) BSA, 0.2% Tween in PBS) andafter washing were revealed with goat anti-human kappa-HRP (CambridgeBioscience 2060-05) in sample-conjugate buffer and TMB with a 2.5M H2504stop solution.

Gut, Mucosa and Serum Levels:

Serum samples collected from blood taken at 168 hour time point andcolon samples were removed after this.

20mg/kg IP at 168 hour Sample ng/mL per cm mucosa serum μg/mL 1001 23.275.0 1002 13.7 90.8 1003 21.8 70.5 1004 53.8 119.4

20mg/kg SC at 168 hour Sample ng/mL per cm mucosa serum μg/mL 2001 41.4108.7 2002 62.1 76.6 2003 35.6 163.7 2004 37.3 153.3

Serum Data Hamster i.p. Hamster s.c. SE of SE of Mean mean Mean meanC_(max): μg/mL 202 12 186 21 T_(max): hr 36 7 76 16 AUC _((last)): hr ·μg/mL 22626 1378 22371 2258 AUC _((inf)): hr · μg/mL 43287 7169 6129017637 % Extrapolation: 43.7 9.2 54 11.7 CL/F mL/hr/kg 0.50 0.07 0.430.13 MRT_(inf) h 223 53 310 88 t_(1/2,z): h 149.2 36.9 188.5 61.9

The data is also shown in FIGS. 70 and 71

Hamster ID Mean SE IP serum kinetics C_(max): μg/mL 202 12 T_(max): hr36 7 AUC_((last)): hr · μg/mL 22626 1378 AUC_((inf)): hr · μg/mL 432877169 % Extrapolation: 43.7 9.2 CL/F mL/hr/kg 0.50 0.07 MRT_(inf) h 22353 t_(1/2,z): h 149.2 36.9 SC serum kinetics Hamster ID Mean SE C_(max):μg/mL 186 21 T_(max): hr 76 16 AUC_((last)): hr · μg/mL 22371 2258AUC_((inf)): hr · μg/mL 61290 17637 % Extrapolation: 54 11.7 CL/FmL/hr/kg 0.43 0.13 MRT_(inf) h 310 88 t_(1/2): h 188.5 61.9

It was also shown that hIgG1 could be found in ‘scrapings’ of the guti.e that hIgG1 gets into the vasculature of healthy gut—and so could beprotective in ‘prophylactic dosing’. This effect would be even moreprofound in humans since they have a cognate hFcRn.

Example 12 Serum Levels in Hamsters with C. difficile Infection

This study was to determine the serum concentration of CA725.0, CA726.0,CA997.g1 CA1125.g2, and CA01151.g4 following i.p. administration(various doses detailed below) in the Golden Syrian Hamster.

Humanised Mabs were quantified using liquid chromatography tandem massspectrometry (LC-MS/MS) analysis following tryptic digestion.Quantitation was achieved by comparison to authentic standard materialspiked at known concentrations into blank matrix, with spiked horsemyoglobin used as the internal standard.

A unique (“proteotypic”) peptide common to all of the humanised Mabsinvestigated was selected (DTLMISR, a CH2 region peptide) and bothsamples and calibration samples were tryptically digested as outlined.Tryptic digest of 5 μl serum samples was performed overnight usingsequencing grade modified Trypsin (Promega, Southampton, UK) followingdenaturation/reduction with acetonitrile/Tris (2-carboxyethyl) phosphineand carbamido-methylation with iodoacetamide (Sigma-Aldrich, Poole, UK).

The LC-MS/MS system consisted of a CTC HTS-x Autosampler (CTC Analytics,Zwingen, Switzerland), a Agilent 1290 LC system (Agilent Technologies,Stockport, UK) and a Sciex 5500 QTrap MS system (AB Sciex, Warrington,UK), equipped with a Turbo V ion source operated in electrospray mode.Analytes were separated using an Onyx Monolithic C18 column (100×4.6 mm,Phenomenex, Macclesfield, UK) with a gradient of 2 to 95% (v/v)water/acetonitrile (0.1% formic acid) delivered at 1.5 mL/min over 6minutes. The injection volume was 10 μL; all of the eluent wasintroduced into the mass spectrometer source. The source temperature ofthe mass spectrometer was maintained at 600° C. and other sourceparameters (e.g. collision energy, declustering potential, curtain gaspressure etc.) were optimized to achieve maximum sensitivity for thepeptide of interest. Selective transitions for each proteotypic peptideof interest were monitored. Unique (“proteotypic) peptides were selectedfor all of the analytes of interest; samples were analysed followingtryptic digestion.

Plasma concentrations calculated based on the peptides monitored areoutlined below.

For CA164_00997 and CA164_01151, interfering peaks were observed in theMRM traces. For this reason, these two analytes could not be quantifiedin the samples.

Total h-IgG was quantified in all samples using a peptide common to allanalytes of interest. This was done using a combined standard curve ofall five analytes. The validity of this approach is demonstrated by thefact that the sum of the concentrations observed for CA164_00725 andCA164_00726 are in good agreement (within experimental error) of theconcentration observed for total h-IgG.

Using this approach, the total concentration of h-IgG in the samples ofanimals dosed with CA164_00997, CA164_01125 and CA164_01151 wasdetermined.

Overall the data obtained indicate that the exposure of all fiveanalytes of interest was similar for a given dose.

Study groups Blinded labels Treatment components Grp Treatment ActualTreatments Dose days Anti-toxin A Anti-toxin B 4 Treatment3 Vehicle PBS5 mL/kg i.p. 3, −2, −1, 0 2 Vancomycin Vancomycin 5 1, 2, 3, 4, 5 mg/kgb.i.d. p.o. 1 Treatment1 UCB LD* 3, −2, −1, 0 CA997.g1_P3 CA1125.g2_P3CA1151.g4_P3 5 mg/kg A 5 mg/kg i.p. 5 mg/kg 2.5 mg/kg 2.5 mg/kg 5Treatment4 UCB HD* 3, −2, −1, 0 CA997.g1_P3 CA1125.g2_P3 CA1151.g4_P3 50mg/kg A 50 mg/kg i.p. 50 mg/kg 25 mg/kg 25 mg/kg 6 Treatment5CompetitorLD* 3, −2, −1, 0 CA726_P3 CA725_P3 5 mg/kg A 5 mg/kg i.p. 5mg/kg 5 mg/kg 3 Treatment2 CompetitorHD* 3, −2, −1, 0 CA726_P3 CA725_P350 mg/kg A 50 mg/kg i.p. 50 mg/kg 50 mg/kg

TABLE 19 Group/ Animal Serum conc time Day No Dose μg/mLtotal h-IgG 1 144 5 mg/kg 997, 280 1 45 2.5 mg/kg 302 1 46 1125,2.5 182 6 45 mg/kg 115161 6 47 71 6 49 45 3 1 60 50 mg/kg 3040 1 61 725, 3330 1 62 50 mg/kg2990 6 62 726 583 6 63 913 6 64 1240 28 64 199 28 65 36 4 1 71 Vehiclend 1 72 nd 1 73 nd 5 1 82 50 mg/kg 3050 1 83 997, 2790 1 84 25 mg/kg2370 6 82 1125,25 838 6 83 mg/kg 1151 645 6 84 855 28 82 116 28 83 65 2884 66 28 85 44 28 86 101 28 87 89 28 88 27 28 89 31 28 90 66 6 1 93 5mg/kg 725, 335 1 94 5 mg/kg 726 322 1 95 260 6 200 103 6 202 62 6 203 7928 203 nd nd - not detected (LOQ = 2.5 μg/mL for all analytes na - notanalysed: interference in the sample was observed for 997 and 1151

TABLE 20 Antibody CA725 is prior art antibody MDX1388. Antibody CA726 isprior art antibody CDA1 as described (15) A summary of this data ispresented in FIG. 72. Small intestine Caecal pathology pathology DarkDark Group Black Red Red Pink Normal Red Red PBS control 1 9 1 0 0 0 1MDX high 0 1 4 4 2 1 0 50 mg/Kg x4 UCB high 0 0 1 1 9 0 0 50 mg/Kg x4

REFERENCES

-   1. Kuehne, S et al., “The role of toxin A and toxin B in Clostridium    difficile Infection” Nature (2010) 467: 711-713.-   2. Davies A H et al., “Super toxins from a super bug: structure and    function of Clostridium difficile toxins” Biochem. J (2011) 436:    517-526.-   3. Rothman, S et al., “Differential Cytotoxic Effects of Toxins A    and B Isolated from Clostridium difficile” Infect. Imm. (1984) 46:    324-331.-   4. Du, T and Alfa, M J “Translocation of Clostridium difficile toxin    B across polarized Caco-2 cell monolayers is enhanced by toxin A”    Can J Infect Dis. (2004) 15: 83-88.-   5. Kim, Iaconis and Rolfe. “Immunization of Adult Hamsters against    Clostridium difficile-Associated Ileocecitis and Transfer of    Protection to Infant Hamsters” Infect. Imm. (1987) 55:2984-2992-   6. Rupnik J C M (2003) 41:1118-1125-   7. Chaves-Olarte J B C (1999) 274:11046-11052.-   8. Lylerly, D M et al., “Passive Immunization of Hamsters against    Disease Caused by Clostridium difficile by Use of Bovine    Immunoglobulin G Concentrate” Infection and Immunity (1991)    59:2215-2218.-   9. Lylerly, D M et al., “Vaccination against Lethal Clostridium    difficile Enterocolitis with a Nontoxic Recombinant Peptide of Toxin    A” Current Microbiology (1990) 21:29-32.-   10. Lylerly, D M et al., “Characterization of Toxins A and B of    Clostridium difficile with Monoclonal Antibodies” Infect.    Imm. (1986) 54:70-76.-   11. Corthier et al., “Protection against Experimental    Pseudomembranous Colitis in Gnotobiotic Mice by Use of Monoclonal    Antibodies against Clostridium difficile Toxin A” Infect.    Imm. (1991) 59: 1192-1195.-   12. Kink J A and Williams J A, “Antibodies to Recombinant    Clostridium difficile Toxins A and B Are an Effective Treatment and    Prevent Relapse of C. difficile-Associated Disease in a Hamster    Model of Infection” Infect. Imm. (1998) 66:2018-2025.-   13. Ma D, et al., Progenics inc. ASM Poster 27 May 2010-   14. Hansen, G and Demarest, S J. WO 2006/0718877 A2-   15. Babcock G J, et al., “Human monoclonal antibodies directed    against toxins A and B prevent Clostridium difficile-induced    mortality in hamster” Infect. Imm. (2006) 74:6339-6347.-   16. Lowy I et al., “Treatment with Monoclonal Antibodies against    Clostridium difficile Toxins” NEJM (2010) 362: 197-205.-   17. Zubler, R. H., Erard, F., Lees, R. K., Van, L. M., Mingari, C.,    Moretta, L. & MacDonald, H. R. (1985). Mutant EL-4 thymoma cells    polyclonally activate murine and human B cells via direct cell    interaction. J. Immunol. 134, 3662-3668-   18. Babcook, J. S., Leslie, K. B., Olsen, O. A., Salmon, R. A. &    Schrader, J. W. (1996). A novel strategy for generating monoclonal    antibodies from single, isolated lymphocytes producing antibodies of    defined specificities. Proc. Natl. Acad. Sci. U.S.A 93, 7843-7848-   19. Tickle, S., Adams, R., Brown, D., Griffiths, M., Lightwood, D. &    Lawson, A. (2010). High-Throughput Screening for High Affinity    Antibodies., pp. 303-307.-   20. Demarest et al., mAbs (2010) 2:190-198-   21. Yoshida et al., J. Clin. Invest. (2006) 116: 2142-2151-   22. Xu et al., Vaccine (2005) 23:2658-2664.-   23. Yousaf et al., Clin. Exp. Immunol. (1986) 66:654-660-   24. Mannik et al., J. Exp. Med. (1971) 133: 713-739-   25. Nusrat et al., Infection and Immunity (2001) 69:1329-1336-   26. Lima et al., Infect Immun (1988) 56:582-588-   27. Ravichandran et al J of Pharmacology and Experimental    Therapeutics. (2006) 318: 1343-1351-   28. Takahashi et al., (2009) Vaccine 27:2616-2619-   29. Cohen et al., Infect. Cont. and Hosp. Epidem. (2010) 31: 431-455-   30. Barbut et al., J. Clin. Microbiol. (2000) 38: 2386-2388-   31. Wilcox et al., J. Hospital Infection (1998) 38: 93-100.

1-41. (canceled)
 42. A pharmaceutical composition comprising one or moremonoclonal antibodies specific to antigen TcdB1234 wherein the antibodyhas high affinity of 600 pM or less for the target antigen TcdB1234 andsaid one or more monoclonal antibodies are independently selected from:i) a heavy chain wherein the variable domain of the heavy chaincomprises a CDR having the sequence given in SEQ ID NO:124 for CDR-H1, aCDR having the sequence given in SEQ ID NO: 125 for CDR-H2 and a CDRhaving the sequence given in SEQ ID NO: 126 for CDR-H3, and a lightchain wherein the variable domain of the light chain comprises a CDRhaving the sequence given in SEQ ID NO:121 for CDR-L1, a CDR having thesequence given in in SEQ ID NO:122 for CDR-L2 and a CDR having thesequence given in SEQ ID NO:123 for CDR-L3; ii) a heavy chain whereinthe variable domain of the heavy chain comprises a CDR having thesequence given in SEQ ID NO:154 for CDR-H1, a CDR having the sequencegiven in SEQ ID NO:155 for CDR-H2 and a CDR having the sequence given inSEQ ID NO:156 for CDR-H3, and a light chain wherein the variable domainof the light chain comprises a CDR having the sequence given in SEQ IDNO:151 for CDR-L1, a CDR having the sequence given in in SEQ ID NO:152for CDR-L2 and a CDR having the sequence given in SEQ ID NO:153 forCDR-L3; iii) a heavy chain wherein the variable domain of the heavychain comprises a CDR having the sequence given in SEQ ID NO:144 forCDR-H1, a CDR having the sequence given in SEQ ID NO:145 for CDR-H2 anda CDR having the sequence given in SEQ ID NO:146 for CDR-H3, and a lightchain wherein the variable domain of the light chain comprises a CDRhaving the sequence given in SEQ ID NO:141 for CDR-L1, a CDR having thesequence given in in SEQ ID NO:142 for CDR-L2 and a CDR having thesequence given in SEQ ID NO:143 for CDR-L3; iv) a heavy chain whereinthe variable domain of the heavy chain comprises a CDR having thesequence given in SEQ ID NO:164 for CDR-H1, a CDR having the sequencegiven in SEQ ID NO:165 for CDR-H2 and a CDR having the sequence given inSEQ ID NO:166 for CDR-H3, and a light chain wherein the variable domainof the light chain comprises a CDR having the sequence given in SEQ IDNO:161 for CDR-L1, a CDR having the sequence given in in SEQ ID NO:162for CDR-L2 and a CDR having the sequence given in SEQ ID NO:163 forCDR-L3; v) a heavy chain wherein the variable domain of the heavy chaincomprises a CDR having the sequence given in SEQ ID NO:64 for CDR-H1, aCDR having the sequence given in SEQ ID NO: 65 for CDR-H2 and a CDRhaving the sequence given in SEQ ID NO: 66 for CDR-H3, and a light chainwherein the variable domain of the light chain comprises a CDR havingthe sequence given in SEQ ID NO:61 for CDR-L1, a CDR having the sequencegiven in in SEQ ID NO:62 for CDR-L2 and a CDR having the sequence givenin SEQ ID NO:63 for CDR-L3; vi) a heavy chain wherein the variabledomain of the heavy chain comprises a CDR having the sequence given inSEQ ID NO:74 for CDR-H1, a CDR having the sequence given in SEQ ID NO:75 for CDR-H2 and a CDR having the sequence given in SEQ ID NO: 76 forCDR-H3, and a light chain wherein the variable domain of the light chaincomprises a CDR having the sequence given in SEQ ID NO:71 for CDR-L1, aCDR having the sequence given in in SEQ ID NO:72 for CDR-L2 and a CDRhaving the sequence given in SEQ ID NO:73 for CDR-L3; vii) a heavy chainwherein the variable domain of the heavy chain comprises a CDR havingthe sequence given in SEQ ID NO:84 for CDR-H1, a CDR having the sequencegiven in SEQ ID NO: 85 for CDR-H2 and a CDR having the sequence given inSEQ ID NO: 86 for CDR-H3, and a light chain wherein the variable domainof the light chain comprises a CDR having the sequence given in SEQ IDNO:81 for CDR-L1, a CDR having the sequence given in in SEQ ID NO:82 forCDR-L2 and a CDR having the sequence given in SEQ ID NO:83 for CDR-L3;viii) a heavy chain wherein the variable domain of the heavy chaincomprises a CDR having the sequence given in SEQ ID NO:134 for CDR-H1, aCDR having the sequence given in SEQ ID NO: 135 for CDR-H2 and a CDRhaving the sequence given in SEQ ID NO: 136 for CDR-H3, and a lightchain wherein the variable domain of the light chain comprises a CDRhaving the sequence given in SEQ ID NO:131 for CDR-L1, a CDR having thesequence given in in SEQ ID NO:132 for CDR-L2 and a CDR having thesequence given in SEQ ID NO:133 for CDR-L3.
 43. A pharmaceuticalcomposition according to claim 42, wherein said one or more monoclonalantibodies are independently selected from: i) a heavy chain wherein thevariable domain of the heavy chain comprises a CDR having the sequencegiven in SEQ ID NO:124 for CDR-H1, a CDR having the sequence given inSEQ ID NO: 125 for CDR-H2 and a CDR having the sequence given in SEQ IDNO: 126 for CDR-H3, and a light chain wherein the variable domain of thelight chain comprises a CDR having the sequence given in SEQ ID NO:121for CDR-L1, a CDR having the sequence given in in SEQ ID NO:122 forCDR-L2 and a CDR having the sequence given in SEQ ID NO:123 for CDR-L3;ii) a heavy chain wherein the variable domain of the heavy chaincomprises a CDR having the sequence given in SEQ ID NO:154 for CDR-H1, aCDR having the sequence given in SEQ ID NO:155 for CDR-H2 and a CDRhaving the sequence given in SEQ ID NO:156 for CDR-H3, and a light chainwherein the variable domain of the light chain comprises a CDR havingthe sequence given in SEQ ID NO:151 for CDR-L1, a CDR having thesequence given in in SEQ ID NO:152 for CDR-L2 and a CDR having thesequence given in SEQ ID NO:153 for CDR-L3; iii) a heavy chain whereinthe variable domain of the heavy chain comprises a CDR having thesequence given in SEQ ID NO:144 for CDR-H1, a CDR having the sequencegiven in SEQ ID NO:145 for CDR-H2 and a CDR having the sequence given inSEQ ID NO:146 for CDR-H3, and a light chain wherein the variable domainof the light chain comprises a CDR having the sequence given in SEQ IDNO:141 for CDR-L1, a CDR having the sequence given in in SEQ ID NO:142for CDR-L2 and a CDR having the sequence given in SEQ ID NO:143 forCDR-L3; and iv) a heavy chain wherein the variable domain of the heavychain comprises a CDR having the sequence given in SEQ ID NO:164 forCDR-H1, a CDR having the sequence given in SEQ ID NO:165 for CDR-H2 anda CDR having the sequence given in SEQ ID NO:166 for CDR-H3, and a lightchain wherein the variable domain of the light chain comprises a CDRhaving the sequence given in SEQ ID NO:161 for CDR-L1, a CDR having thesequence given in in SEQ ID NO:162 for CDR-L2 and a CDR having thesequence given in SEQ ID NO:163 for CDR-L3.
 44. A pharmaceuticalcomposition according to claim 42, wherein a monoclonal antibody whichspecifically binds TcdB1234 comprises a heavy chain wherein the variabledomain of the heavy chain comprises a CDR having the sequence given inSEQ ID NO:124 for CDR-H1, a CDR having the sequence given in SEQ ID NO:125 for CDR-H2 and a CDR having the sequence given in SEQ ID NO: 126 forCDR-H3, and a light chain wherein the variable domain of the light chaincomprises a CDR having the sequence given in SEQ ID NO:121 for CDR-L1, aCDR having the sequence given in in SEQ ID NO:122 for CDR-L2 and a CDRhaving the sequence given in SEQ ID NO:123 for CDR-L3.
 45. Apharmaceutical composition according to claim 44, wherein the monoclonalantibody has a heavy chain comprising the sequence given in SEQ IDNO:129 and a light chain comprising the sequence given in SEQ ID NO:127.46. A pharmaceutical composition according to claim 42, wherein amonoclonal antibody which specifically binds TcdB1234 comprising a heavychain wherein the variable domain of the heavy chain comprises a CDRhaving the sequence given in SEQ ID NO:154 for CDR-H1, a CDR having thesequence given in SEQ ID NO:155 for CDR-H2 and a CDR having the sequencegiven in SEQ ID NO:156 for CDR-H3, and a light chain wherein thevariable domain of the light chain comprises a CDR having the sequencegiven in SEQ ID NO:151 for CDR-L1, a CDR having the sequence given in inSEQ ID NO:152 for CDR-L2 and a CDR having the sequence given in SEQ IDNO:153 for CDR-L3.
 47. A pharmaceutical composition according to claim46, wherein the monoclonal antibody has a heavy chain comprising thesequence given in SEQ ID NO:159 and a light chain comprising thesequence given in SEQ ID NO:157.
 48. A pharmaceutical compositionaccording to claim 42, wherein the monoclonal antibody has a heavy chaincomprising the sequence given in SEQ ID NO:149 and a light chaincomprising the sequence given in SEQ ID NO:147.
 49. A pharmaceuticalcomposition according to claim 42, wherein the monoclonal antibody has aheavy chain comprising the sequence given in SEQ ID NO:169 and a lightchain comprising the sequence given in SEQ ID NO:167.
 50. Apharmaceutical composition according to claim 42, wherein at least oneof said monoclonal antibodies is a neutralizing antibody which iseffective against ribotypes
 003. 51. A pharmaceutical compositionaccording to claim 42, further comprising two or more antibodiesspecific to TcdB.
 52. A pharmaceutical composition according to claim42, further comprising one or more antibodies specific to TcdA.
 53. Apharmaceutical composition according to claim 52, wherein the antibodywhich specifically binds TcdA comprises a heavy chain sequence given inSEQ ID NO: 19 and a light chain sequence given in SEQ ID NO:
 17. 54. Apharmaceutical composition according to claim 52, wherein the antibodywhich specifically binds TcdA comprises a heavy chain sequence given inSEQ ID NO: 29 and a light chain sequence given in SEQ ID NO:
 27. 55. Apharmaceutical composition according to claim 52, wherein the antibodywhich specifically binds TcdA comprises a heavy chain sequence given inSEQ ID NO: 49 and a light chain sequence given in SEQ ID NO:
 47. 56. Apharmaceutical composition according to claim 52, wherein the antibodywhich specifically binds TcdA comprises a heavy chain sequence given inSEQ ID NO: 59 and a light chain sequence given in SEQ ID NO:
 57. 57. Apharmaceutical composition according to claim 52, wherein the antibodywhich specifically binds TcdA comprises a heavy chain sequence given inSEQ ID NO: 39 and a light chain sequence given in SEQ ID NO:
 37. 58. Apharmaceutical composition according to claim 52, wherein the antibodywhich specifically binds TcdA comprises a heavy chain sequence given inSEQ ID NO: 9 and a light chain sequence given in SEQ ID NO:
 7. 59. Apharmaceutical composition according to claim 52, which furthercomprises a pharmaceutically acceptable excipient.
 60. A method oftreatment or prophylaxis of Clostridium difficile infection orcomplications therefrom comprising administering a pharmaceuticalcomposition as defined in claim 42 to a patient in need thereof.
 61. Amethod according to claim 60, wherein the composition isco-administrated with a compound selected the group comprisingmetronidazole, vancomycin, clindamycin, fidaxomicin and combinationsthereof.